Latest versions of pip starting from v10.0 changed parts of their APIs. That’s why several older versions of PyCharm became incompatible with the newer pip versions. If you use previous PyCharm versions and want to use latest versions of pip, please update PyCharm. Here’s the list of Pycharm versions updated:
If you’re using a version with a minor update (last number) lower than those mentioned, please update PyCharm. If you wish to update to the latest version (2018.1.3 at the time of writing), get it here. If you wish to get one of the hotfixed older versions, you can find the appropriate release on our previous versions page.