[BUG] using -v and -e connected (as -ve) fails in 3.8.0

[harpaj]

In our CI environment, we start tox like tox -vve py27.
This worked before the release of 3.8.0 without problems, but now fails with this error:

$ tox -vve py27
usage: tox [-v] [-q]
tox: error: argument -v: ignored explicit argument 'e'

tox -vv -e py27 still works without problem, so it's not a big issue; but as it breaks backwards compatibility, it might at least warrant a message in the release notes.

[gaborbernat]

😢 seems https://docs.python.org/3.4/library/argparse.html#argparse.ArgumentParser.parse_known_args is not smart enough to parse that; we'll need to catch the error and ignore it (while redirecting the output to null - as the error message is non optional) - related section https://github.com/tox-dev/tox/blob/master/src/tox/session/__init__.py#L45-L52

16.4. argparse — Parser for command-line options, arguments and sub-commands — Python 3.4.10 documentation

[rpkilby]

The prefix matching behavior can be disabled in Python 3.5+ with allow_abbrev=False. Of course, this doesn't help Python 3.4 and earlier, but Python 3.4 is now EOL and Python 2.7 is EOL at the end of the year? Meh? ¯\_(ツ)_/¯

[gaborbernat]

@rpkilby sadly that does not help us, disable-ing the abbreviation will also disable detecting the -v flags passed in the above which is the whole goal. At that point, we might just suppress the error.