cli shouldn't mess with sys.argv

[davidism]

Just merged pallets/werkzeug#1416 so Werkzeug's reloader detects python -m module correctly. All of flask.cli.main() can be replaced with:

def main(as_module=False):
    cli.main(prog_name="python -m flask" if as_module else None)

Need to wait until Werkzeug 0.15 has been out for a bit before we can bump Flask's min version.

[seawolf42]

picking up this task

[EtiennePelletier]

PR #3181 updates Werkzeug to >=0.15, so once merged I'll take care of this ticket.

[seawolf42]

@EtiennePelletier if you're going to do it, you don't need to wait for the other to be merged, but you should reference that PR (using the # reference like above) in the new PR so that they see the dependency when they review this one.

[EtiennePelletier]

Alright! I just wanted to avoid bumping Werkzeug's version in setup.py again since master is currently referencing 0.14. I'll leave it as is and explicitly mention it in the PR.