BUG: Use return codes properly, add --count

[larsoner]

Use standard return codes:

1. Return 2 64 instead of 1 for bad usage
2. Return 1 65 when there are spelling errors
3. Add --count to print to the last line of stderr the number of errors (like flake8); should allow easy-ish fixes for people who actually want the count

Adds a wrapper to our tests that goes and grabs the capsys output from one stack frame higher so that a ton of lines didn't have to change.

Closes #1495.

@vinc17fr @craigbarnes @kkirsche WDYT?

[kkirsche]

LGTM

[peternewman]

A few initial comments

[peternewman]

Some more comments.

Also I wonder if given the exit and count behaviour changes, and some of the other changes that have gone in recently, whether the next release should be a major version bump?

[kkirsche]

If using semver it should be a major as it’s a breaking API change

[peternewman]

Sorry @larsoner , you probably want to revert a lot of 7157f15 . I was looking for consistency and assumed sentence case, but looking at ls and flake8 their help strings are lower case.

[larsoner]

Okay to merge now that all help entries start with lower case @peternewman ?

[peternewman]

LGTM

[peternewman]

Do you want to see if @craigbarnes has further feedback or @vinc17fr has any.

Also as @kkirsche and I both commented, please can we bump the major version in this PR.

[larsoner]

please can we bump the major version in this PR.

Done

[craigbarnes]

LGTM.