We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
`python3.7` raises `flake8` warning
It is a bug in `flake8`:
- https://github.com/PyCQA/pycodestyle/issues/728

We currently allow `python3.7` build to fail.

```
=============================== warnings summary ===============================
tests/test_visitors/test_wrong_class/test_base_class.py::FLAKE8
  /home/travis/virtualenv/python3.7.0/lib/python3.7/site-packages/pycodestyle.py:113: FutureWarning: Possible nested set at position 1
    EXTRANEOUS_WHITESPACE_REGEX = re.compile(r'[[({] | []}),;:]')
-- Docs: https://docs.pytest.org/en/latest/warnings.html
=================== 1514 passed, 1 warnings in 27.96 seconds ===================
```

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `wemake_python_styleguide/compat.py`
Content:
```
1 # -*- coding: utf-8 -*-
2 
3 """
4 This module contains ugly hacks and fixes for version compat issues.
5 
6 Do not be over-exited to add anything here.
7 """
8 
9 import ast
10 
11 
12 def maybe_set_parent(tree: ast.AST) -> ast.AST:
13     """Sets parents for all nodes that do not have this prop."""
14     for statement in ast.walk(tree):
15         for child in ast.iter_child_nodes(statement):
16             if not hasattr(child, 'parent'):  # noqa: Z113
17                 setattr(child, 'parent', statement)
18 
19     return tree
20
```

Path: `wemake_python_styleguide/checker.py`
Content:
```
1 # -*- coding: utf-8 -*-
2 
3 from ast import Module
4 from typing import Generator
5 
6 from flake8.options.manager import OptionManager
7 
8 from wemake_python_styleguide import constants
9 from wemake_python_styleguide.compat import maybe_set_parent
10 from wemake_python_styleguide.options.config import Configuration
11 from wemake_python_styleguide.types import (
12     CheckerSequence,
13     CheckResult,
14     ConfigurationOptions,
15 )
16 from wemake_python_styleguide.version import version
17 from wemake_python_styleguide.visitors.ast.complexity.counts import (
18     MethodMembersVisitor,
19     ModuleMembersVisitor,
20 )
21 from wemake_python_styleguide.visitors.ast.complexity.function import (
22     FunctionComplexityVisitor,
23 )
24 from wemake_python_styleguide.visitors.ast.complexity.nested import (
25     NestedComplexityVisitor,
26 )
27 from wemake_python_styleguide.visitors.ast.complexity.offset import (
28     OffsetVisitor,
29 )
30 from wemake_python_styleguide.visitors.ast.wrong_class import WrongClassVisitor
31 from wemake_python_styleguide.visitors.ast.wrong_contents import (
32     WrongContentsVisitor,
33 )
34 from wemake_python_styleguide.visitors.ast.wrong_function_call import (
35     WrongFunctionCallVisitor,
36 )
37 from wemake_python_styleguide.visitors.ast.wrong_import import (
38     WrongImportVisitor,
39 )
40 from wemake_python_styleguide.visitors.ast.wrong_keyword import (
41     WrongKeywordVisitor,
42     WrongRaiseVisitor,
43 )
44 from wemake_python_styleguide.visitors.ast.wrong_name import (
45     WrongModuleMetadataVisitor,
46     WrongNameVisitor,
47 )
48 from wemake_python_styleguide.visitors.ast.wrong_string import (
49     WrongStringVisitor,
50 )
51 from wemake_python_styleguide.visitors.filenames.wrong_module_name import (
52     WrongModuleNameVisitor,
53 )
54 
55 #: Visitors that should be working by default:
56 ENABLED_VISITORS: CheckerSequence = [
57     # Styling and correctness:
58     WrongRaiseVisitor,
59     WrongFunctionCallVisitor,
60     WrongImportVisitor,
61     WrongKeywordVisitor,
62     WrongNameVisitor,
63     WrongModuleMetadataVisitor,
64     WrongClassVisitor,
65     WrongStringVisitor,
66     WrongContentsVisitor,
67 
68     # Complexity:
69     FunctionComplexityVisitor,
70     NestedComplexityVisitor,
71     OffsetVisitor,
72     ModuleMembersVisitor,
73     MethodMembersVisitor,
74 
75     # Modules:
76     WrongModuleNameVisitor,
77 ]
78 
79 
80 class Checker(object):
81     """
82     Main checker class.
83 
84     Runs all checks that are bundled with this package.
85     If you want to add new checks they should be added to ``ENABLED_VISITORS``.
86     """
87 
88     name = 'wemake-python-styleguide'
89     version = version
90 
91     config = Configuration()
92     options: ConfigurationOptions
93 
94     def __init__(self, tree: Module, filename: str = constants.STDIN) -> None:
95         """Creates new checker instance."""
96         self.tree = maybe_set_parent(tree)
97         self.filename = filename
98 
99     @classmethod
100     def add_options(cls, parser: OptionManager) -> None:
101         """Calls Configuration instance method for registering options."""
102         cls.config.register_options(parser)
103 
104     @classmethod
105     def parse_options(cls, options: ConfigurationOptions) -> None:
106         """Parses registered options for providing to the visitor."""
107         cls.options = options
108 
109     def run(self) -> Generator[CheckResult, None, None]:
110         """
111         Runs the checker.
112 
113         This method is used by `flake8` API.
114         After all configuration is parsed and passed.
115         """
116         for visitor_class in ENABLED_VISITORS:
117             visitor = visitor_class(
118                 self.options,
119                 tree=self.tree,
120                 filename=self.filename,
121             )
122             visitor.run()
123 
124             for error in visitor.errors:
125                 yield (*error.node_items(), type(self))
126
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/wemake_python_styleguide/checker.py b/wemake_python_styleguide/checker.py
--- a/wemake_python_styleguide/checker.py
+++ b/wemake_python_styleguide/checker.py
@@ -6,7 +6,6 @@
 from flake8.options.manager import OptionManager
 
 from wemake_python_styleguide import constants
-from wemake_python_styleguide.compat import maybe_set_parent
 from wemake_python_styleguide.options.config import Configuration
 from wemake_python_styleguide.types import (
     CheckerSequence,
@@ -93,7 +92,7 @@
 
     def __init__(self, tree: Module, filename: str = constants.STDIN) -> None:
         """Creates new checker instance."""
-        self.tree = maybe_set_parent(tree)
+        self.tree = tree
         self.filename = filename
 
     @classmethod
diff --git a/wemake_python_styleguide/compat.py b/wemake_python_styleguide/compat.py
deleted file mode 100644
--- a/wemake_python_styleguide/compat.py
+++ /dev/null
@@ -1,19 +0,0 @@
-# -*- coding: utf-8 -*-
-
-"""
-This module contains ugly hacks and fixes for version compat issues.
-
-Do not be over-exited to add anything here.
-"""
-
-import ast
-
-
-def maybe_set_parent(tree: ast.AST) -> ast.AST:
-    """Sets parents for all nodes that do not have this prop."""
-    for statement in ast.walk(tree):
-        for child in ast.iter_child_nodes(statement):
-            if not hasattr(child, 'parent'):  # noqa: Z113
-                setattr(child, 'parent', statement)
-
-    return tree

{"golden_diff": "diff --git a/wemake_python_styleguide/checker.py b/wemake_python_styleguide/checker.py\n--- a/wemake_python_styleguide/checker.py\n+++ b/wemake_python_styleguide/checker.py\n@@ -6,7 +6,6 @@\n from flake8.options.manager import OptionManager\n \n from wemake_python_styleguide import constants\n-from wemake_python_styleguide.compat import maybe_set_parent\n from wemake_python_styleguide.options.config import Configuration\n from wemake_python_styleguide.types import (\n     CheckerSequence,\n@@ -93,7 +92,7 @@\n \n     def __init__(self, tree: Module, filename: str = constants.STDIN) -> None:\n         \"\"\"Creates new checker instance.\"\"\"\n-        self.tree = maybe_set_parent(tree)\n+        self.tree = tree\n         self.filename = filename\n \n     @classmethod\ndiff --git a/wemake_python_styleguide/compat.py b/wemake_python_styleguide/compat.py\ndeleted file mode 100644\n--- a/wemake_python_styleguide/compat.py\n+++ /dev/null\n@@ -1,19 +0,0 @@\n-# -*- coding: utf-8 -*-\n-\n-\"\"\"\n-This module contains ugly hacks and fixes for version compat issues.\n-\n-Do not be over-exited to add anything here.\n-\"\"\"\n-\n-import ast\n-\n-\n-def maybe_set_parent(tree: ast.AST) -> ast.AST:\n-    \"\"\"Sets parents for all nodes that do not have this prop.\"\"\"\n-    for statement in ast.walk(tree):\n-        for child in ast.iter_child_nodes(statement):\n-            if not hasattr(child, 'parent'):  # noqa: Z113\n-                setattr(child, 'parent', statement)\n-\n-    return tree\n", "issue": "`python3.7` raises `flake8` warning\nIt is a bug in `flake8`:\r\n- https://github.com/PyCQA/pycodestyle/issues/728\r\n\r\nWe currently allow `python3.7` build to fail.\r\n\r\n```\r\n=============================== warnings summary ===============================\r\ntests/test_visitors/test_wrong_class/test_base_class.py::FLAKE8\r\n  /home/travis/virtualenv/python3.7.0/lib/python3.7/site-packages/pycodestyle.py:113: FutureWarning: Possible nested set at position 1\r\n    EXTRANEOUS_WHITESPACE_REGEX = re.compile(r'[[({] | []}),;:]')\r\n-- Docs: https://docs.pytest.org/en/latest/warnings.html\r\n=================== 1514 passed, 1 warnings in 27.96 seconds ===================\r\n```\n", "before_files": [{"content": "# -*- coding: utf-8 -*-\n\n\"\"\"\nThis module contains ugly hacks and fixes for version compat issues.\n\nDo not be over-exited to add anything here.\n\"\"\"\n\nimport ast\n\n\ndef maybe_set_parent(tree: ast.AST) -> ast.AST:\n    \"\"\"Sets parents for all nodes that do not have this prop.\"\"\"\n    for statement in ast.walk(tree):\n        for child in ast.iter_child_nodes(statement):\n            if not hasattr(child, 'parent'):  # noqa: Z113\n                setattr(child, 'parent', statement)\n\n    return tree\n", "path": "wemake_python_styleguide/compat.py"}, {"content": "# -*- coding: utf-8 -*-\n\nfrom ast import Module\nfrom typing import Generator\n\nfrom flake8.options.manager import OptionManager\n\nfrom wemake_python_styleguide import constants\nfrom wemake_python_styleguide.compat import maybe_set_parent\nfrom wemake_python_styleguide.options.config import Configuration\nfrom wemake_python_styleguide.types import (\n    CheckerSequence,\n    CheckResult,\n    ConfigurationOptions,\n)\nfrom wemake_python_styleguide.version import version\nfrom wemake_python_styleguide.visitors.ast.complexity.counts import (\n    MethodMembersVisitor,\n    ModuleMembersVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.function import (\n    FunctionComplexityVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.nested import (\n    NestedComplexityVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.offset import (\n    OffsetVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_class import WrongClassVisitor\nfrom wemake_python_styleguide.visitors.ast.wrong_contents import (\n    WrongContentsVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_function_call import (\n    WrongFunctionCallVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_import import (\n    WrongImportVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_keyword import (\n    WrongKeywordVisitor,\n    WrongRaiseVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_name import (\n    WrongModuleMetadataVisitor,\n    WrongNameVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_string import (\n    WrongStringVisitor,\n)\nfrom wemake_python_styleguide.visitors.filenames.wrong_module_name import (\n    WrongModuleNameVisitor,\n)\n\n#: Visitors that should be working by default:\nENABLED_VISITORS: CheckerSequence = [\n    # Styling and correctness:\n    WrongRaiseVisitor,\n    WrongFunctionCallVisitor,\n    WrongImportVisitor,\n    WrongKeywordVisitor,\n    WrongNameVisitor,\n    WrongModuleMetadataVisitor,\n    WrongClassVisitor,\n    WrongStringVisitor,\n    WrongContentsVisitor,\n\n    # Complexity:\n    FunctionComplexityVisitor,\n    NestedComplexityVisitor,\n    OffsetVisitor,\n    ModuleMembersVisitor,\n    MethodMembersVisitor,\n\n    # Modules:\n    WrongModuleNameVisitor,\n]\n\n\nclass Checker(object):\n    \"\"\"\n    Main checker class.\n\n    Runs all checks that are bundled with this package.\n    If you want to add new checks they should be added to ``ENABLED_VISITORS``.\n    \"\"\"\n\n    name = 'wemake-python-styleguide'\n    version = version\n\n    config = Configuration()\n    options: ConfigurationOptions\n\n    def __init__(self, tree: Module, filename: str = constants.STDIN) -> None:\n        \"\"\"Creates new checker instance.\"\"\"\n        self.tree = maybe_set_parent(tree)\n        self.filename = filename\n\n    @classmethod\n    def add_options(cls, parser: OptionManager) -> None:\n        \"\"\"Calls Configuration instance method for registering options.\"\"\"\n        cls.config.register_options(parser)\n\n    @classmethod\n    def parse_options(cls, options: ConfigurationOptions) -> None:\n        \"\"\"Parses registered options for providing to the visitor.\"\"\"\n        cls.options = options\n\n    def run(self) -> Generator[CheckResult, None, None]:\n        \"\"\"\n        Runs the checker.\n\n        This method is used by `flake8` API.\n        After all configuration is parsed and passed.\n        \"\"\"\n        for visitor_class in ENABLED_VISITORS:\n            visitor = visitor_class(\n                self.options,\n                tree=self.tree,\n                filename=self.filename,\n            )\n            visitor.run()\n\n            for error in visitor.errors:\n                yield (*error.node_items(), type(self))\n", "path": "wemake_python_styleguide/checker.py"}], "after_files": [{"content": null, "path": "wemake_python_styleguide/compat.py"}, {"content": "# -*- coding: utf-8 -*-\n\nfrom ast import Module\nfrom typing import Generator\n\nfrom flake8.options.manager import OptionManager\n\nfrom wemake_python_styleguide import constants\nfrom wemake_python_styleguide.options.config import Configuration\nfrom wemake_python_styleguide.types import (\n    CheckerSequence,\n    CheckResult,\n    ConfigurationOptions,\n)\nfrom wemake_python_styleguide.version import version\nfrom wemake_python_styleguide.visitors.ast.complexity.counts import (\n    MethodMembersVisitor,\n    ModuleMembersVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.function import (\n    FunctionComplexityVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.nested import (\n    NestedComplexityVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.complexity.offset import (\n    OffsetVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_class import WrongClassVisitor\nfrom wemake_python_styleguide.visitors.ast.wrong_contents import (\n    WrongContentsVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_function_call import (\n    WrongFunctionCallVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_import import (\n    WrongImportVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_keyword import (\n    WrongKeywordVisitor,\n    WrongRaiseVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_name import (\n    WrongModuleMetadataVisitor,\n    WrongNameVisitor,\n)\nfrom wemake_python_styleguide.visitors.ast.wrong_string import (\n    WrongStringVisitor,\n)\nfrom wemake_python_styleguide.visitors.filenames.wrong_module_name import (\n    WrongModuleNameVisitor,\n)\n\n#: Visitors that should be working by default:\nENABLED_VISITORS: CheckerSequence = [\n    # Styling and correctness:\n    WrongRaiseVisitor,\n    WrongFunctionCallVisitor,\n    WrongImportVisitor,\n    WrongKeywordVisitor,\n    WrongNameVisitor,\n    WrongModuleMetadataVisitor,\n    WrongClassVisitor,\n    WrongStringVisitor,\n    WrongContentsVisitor,\n\n    # Complexity:\n    FunctionComplexityVisitor,\n    NestedComplexityVisitor,\n    OffsetVisitor,\n    ModuleMembersVisitor,\n    MethodMembersVisitor,\n\n    # Modules:\n    WrongModuleNameVisitor,\n]\n\n\nclass Checker(object):\n    \"\"\"\n    Main checker class.\n\n    Runs all checks that are bundled with this package.\n    If you want to add new checks they should be added to ``ENABLED_VISITORS``.\n    \"\"\"\n\n    name = 'wemake-python-styleguide'\n    version = version\n\n    config = Configuration()\n    options: ConfigurationOptions\n\n    def __init__(self, tree: Module, filename: str = constants.STDIN) -> None:\n        \"\"\"Creates new checker instance.\"\"\"\n        self.tree = tree\n        self.filename = filename\n\n    @classmethod\n    def add_options(cls, parser: OptionManager) -> None:\n        \"\"\"Calls Configuration instance method for registering options.\"\"\"\n        cls.config.register_options(parser)\n\n    @classmethod\n    def parse_options(cls, options: ConfigurationOptions) -> None:\n        \"\"\"Parses registered options for providing to the visitor.\"\"\"\n        cls.options = options\n\n    def run(self) -> Generator[CheckResult, None, None]:\n        \"\"\"\n        Runs the checker.\n\n        This method is used by `flake8` API.\n        After all configuration is parsed and passed.\n        \"\"\"\n        for visitor_class in ENABLED_VISITORS:\n            visitor = visitor_class(\n                self.options,\n                tree=self.tree,\n                filename=self.filename,\n            )\n            visitor.run()\n\n            for error in visitor.errors:\n                yield (*error.node_items(), type(self))\n", "path": "wemake_python_styleguide/checker.py"}]}