Issues Upgrading from PyQt v5.15.2 to v5.15.3

[Phil Thompson]

A couple of people have reported issues with upgrading PyQt from v5.15.2 
(and earlier) to v5.15.3. This is (IMHO) caused by a bug in pip.

When pip upgrades a package it does the following...

- upgrades any dependencies (including installing new dependencies)
- uninstalls the old version
- installs the new version

...when it should do the following...

- uninstalls the old version
- upgrades any dependencies
- installs the new version

Specifically in this case, pip first installs the wheel (a new 
dependency) containing the Qt libraries. This overwrites the Qt 
libraries from v5.15.2. When pip uninstalls v5.15.2 it removes those 
libraries.

There are two workarounds, remove the old installation first...

pip uninstall PyQt5
pip install PyQt5

...or re-install the wheel containing the Qt libraries...

pip install PyQt5
pip install --force-reinstall PyQt5-Qt

Of course this is only an issue for this particular upgrade - future 
upgrades should behave as normal.

Phil