Stop continuous indexing of libs directory in PyCharm

Any application using Google App Engine requires a directory, 'lib', containing third-party Python libraries. This directory is required by the local development server (dev_appserver.py) and is created by running:

pip install -r requirements.txt -t lib/

However, PyCharm will attempt to index this directory, which takes a significant amount of time.

In order to stop PyCharm from indexing the 'lib' directory, right-click on this directory and select Mark Directory as, then Excluded. This directory will now no longer be indexed by PyCharm.