python commits break CentOS 7 and Fedora 31 python bindings

[Gary Buhrmaster]

The python patches break CentOS 7 and Fedora 31 builds because the new dependency python-uritools (and for CentOS, python-mailer) are simply not available in CentOS 7 and Fedora 31 (possible other distros). For some deb based distros it may be possible to install these dependencies, but not on (at least) these two RH distros.

This breakage can be observed(1) in the buildbot results at ​https://code.mythtv.org/buildbot/#/builders/27/builds/289 (before) and ​https://code.mythtv.org/buildbot/#/builders/27/builds/290 (after) for CentOS 7 and ​https://code.mythtv.org/buildbot/#/builders/121/builds/56 (before) and ​https://code.mythtv.org/buildbot/#/builders/121/builds/57 (after) for Fedora 31.

(1) Since ansible has not been updated(2), these new packages would be unlikely to be installed on those builders in any case, but those packages are simply unavailable on at least some RH based/derived distros.

(2) A missing part of the patch set was updating the ansible tasks to install the new requirement set (which likely would have shown that the dependencies are unobtainable).

[Bill Meek]

For now, anyone else following along can just remove both from configure. Hardware Profile's sendProfile.py will fail. Both will be removed in the fix.

[Bill Meek <billmeek@…>]

In 5bc77ef10/mythtv:

configure: Remove unnecessary Python packages

uritools and email won't be required, although the current
hardwareprofile/sendProfile.py can fail in some cases. This
should allow the Python bindings to build 'til that gets
fixed.

Refs: #13512

[Bill Meek <billmeek@…>]

In 955eb754f5/mythtv:

Python Bindings: Switch default configure selection to python3

Previously, if configure was run without the --python switch, or
if that switch selected a version 3 executable, python2 was used.

python3 is now the default. Using --python=python2 will work, but
it isn't recommended.

Closes: #13512