 class="p">):</span>
    <span class="sd">&#39;&#39;&#39; attempt to get an environment variable. If the variable</span>
<span class="sd">        is not found, None is returned.</span>

<span class="sd">        Parameters</span>
<span class="sd">        ==========</span>
<span class="sd">        variable_key: the variable name</span>
<span class="sd">        required: exit with error if not found</span>
<span class="sd">        silent: Do not print debugging information for variable</span>
<span class="sd">