Use pyupgrade to convert simple string formatting to use f-string
syntax. pyupgrade is intentionally timid and will not create an f-string
if it would make the expression longer or if the substitution parameters
are anything but simple names or dotted names.
* Add failing tests for issue #1139 re: --force-reinstall.
* Address issue #1139: make --force-reinstall not require --upgrade.
* Address review comments.
* Address @xavfernandez's review comments.
This makes the new tests not require network access.