title: 'Cannot setup a Python SDK' in PyCharm project using virtualenv after OS reinstallation
body: <p>I re-installed windows and opened an existing Pycharm project and get the error 'SDK seems invalid' in Settings > Project Interpreter.</p>
  
  <p>The project interpreter path is pointing to python in the venv:</p>
  
  <pre><code>MyProject\venv\Scripts\python.exe
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/wFV76.png" rel="noreferrer"><img src="https://i.stack.imgur.com/wFV76.png" alt="enter image description here"></a></p>
  
  <p>I tried re-adding python.exe:</p>
  
  <p><a href="https://i.stack.imgur.com/amnW0.png" rel="noreferrer"><img src="https://i.stack.imgur.com/amnW0.png" alt="enter image description here"></a></p>
  
  <p>Thats when I get the error:</p>
  
  <p><a href="https://i.stack.imgur.com/8KiuQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/8KiuQ.png" alt="enter image description here"></a></p>
  
  <p><strong>Update:</strong> here is an error from idea.log, a lot of other issues for virtual environments seem to be with windows environment variables and system paths:</p>
  
  <pre><code>2018-09-28 19:50:40,275 [  17601]   INFO - hon.packaging.PyPIPackageCache - Loaded 153296 packages from C:\Users\Matt\.PyCharm2018.2\system\python_packages\pypi-cache.json 
  2018-09-28 19:50:40,816 [  18142]   INFO - rains.python.sdk.PythonSdkType - Fatal Python error: Py_Initialize: unable to load the file system codec
  ModuleNotFoundError: No module named 'encodings'
  
  Current thread 0x00000fa8 (most recent call first):
  
  Exit code -1073740791 
  2018-09-28 19:50:40,816 [  18142]  ERROR - ns.python.sdk.PythonSdkUpdater - Failed to determine Python's sys.path value:
  STDOUT: 
  STDERR: Fatal Python error: Py_Initialize: unable to load the file system codec
  ModuleNotFoundError: No module named 'encodings'
  
  Current thread 0x00000fa8 (most recent call first):
  
  com.jetbrains.python.sdk.InvalidSdkException: Failed to determine Python's sys.path value:
  STDOUT: 
  STDERR: Fatal Python error: Py_Initialize: unable to load the file system codec
  ModuleNotFoundError: No module named 'encodings'
  </code></pre>