Although the issue we've identified with GitHub builds isn't to do with
a python module version it's best to nail precise versions so we can be
sure it will build with the same as we've tested locally.
This remove all dependencies on the keyring lib, updates the
requirements.txt to reflect that, and ensures that setup.py does not
attempt to package it.
Any use of the "old" keyring code will now return None and warn about
its deprecation.
* Removed modules we don't seem to use any more.
* Went through *all* the imports (including 'from X import Y') and
checked every module was one of: builtin, stock in win32 python
3.7.7 or a known dependency of another we do list.
* As we still have the sqlite3.dll hack in setup.py I've only
specified: +py2exe>=0.9.3.2
* certifi==2019.9.11 to work around py2exe issues the current latest
* keyring==19.2.0 to work around py2exe issues the current latest
This still needs testing to see if it's enough to setup an
only-just-installed Python-32 of 3.7.7
