We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
BBAN for en_GB too short
* Faker version: v2.0.3
* OS: linux

Numeric part of the en_GB BBAN needs to be 14 digits long, it currently only returns 13, failing further validation.

### Steps to reproduce

Invoke `fake.iban()` or `fake.bban()` with the en_GB locale, an IBAN or BBAN with 1 digit missing is returned.

### Expected behavior

GB ibans should be 22 chars long: https://www.xe.com/ibancalculator/sample/?ibancountry=united kingdom



--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `faker/providers/bank/en_GB/__init__.py`
Content:
```
1 from .. import Provider as BankProvider
2 
3 
4 class Provider(BankProvider):
5     bban_format = '????#############'
6     country_code = 'GB'
7
```
--- 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/faker/providers/bank/en_GB/__init__.py b/faker/providers/bank/en_GB/__init__.py
--- a/faker/providers/bank/en_GB/__init__.py
+++ b/faker/providers/bank/en_GB/__init__.py
@@ -2,5 +2,5 @@
 
 
 class Provider(BankProvider):
-    bban_format = '????#############'
+    bban_format = '????##############'
     country_code = 'GB'

{"golden_diff": "diff --git a/faker/providers/bank/en_GB/__init__.py b/faker/providers/bank/en_GB/__init__.py\n--- a/faker/providers/bank/en_GB/__init__.py\n+++ b/faker/providers/bank/en_GB/__init__.py\n@@ -2,5 +2,5 @@\n \n \n class Provider(BankProvider):\n-    bban_format = '????#############'\n+    bban_format = '????##############'\n     country_code = 'GB'\n", "issue": "BBAN for en_GB too short\n* Faker version: v2.0.3\r\n* OS: linux\r\n\r\nNumeric part of the en_GB BBAN needs to be 14 digits long, it currently only returns 13, failing further validation.\r\n\r\n### Steps to reproduce\r\n\r\nInvoke `fake.iban()` or `fake.bban()` with the en_GB locale, an IBAN or BBAN with 1 digit missing is returned.\r\n\r\n### Expected behavior\r\n\r\nGB ibans should be 22 chars long: https://www.xe.com/ibancalculator/sample/?ibancountry=united kingdom\r\n\r\n\n", "before_files": [{"content": "from .. import Provider as BankProvider\n\n\nclass Provider(BankProvider):\n    bban_format = '????#############'\n    country_code = 'GB'\n", "path": "faker/providers/bank/en_GB/__init__.py"}], "after_files": [{"content": "from .. import Provider as BankProvider\n\n\nclass Provider(BankProvider):\n    bban_format = '????##############'\n    country_code = 'GB'\n", "path": "faker/providers/bank/en_GB/__init__.py"}]}