Run the 2to3 ws_comma fixer on *.py files. Some lines are now too long
and will need to be broken at some point. OTOH, some lines were already
too long and need to be broken at some point. Now seems as good a time
as any to do this with open PRs at a minimum.

Now is as good a time as any with open PR's at a low.

The current implementation assigns the mask value to a.flat, where a is
the mask being updated. In the scalar case, that is slower than
assigning to a[...], so when a is an instance of int, float, np.bool_,
or np.number use that instead.

WarningManager was a workaround for the lack of the with statement
in Python versions < 2.6. As those versions are no longer supported
it can be removed.

Deprecation notes are added to WarningManager and WarningMessage, but
to avoid a cascade of messages in third party apps, no warnings are
raised at this time, that can be done later.

Closes #3519.

Now that Python < 2.6 is no longer supported we can use the errstate
context manager in places where constructs like
```
    old = seterr(invalid='ignore')
    try:
        blah
    finally:
       seterr(**old)
```
were used.

BUG: np.ma.compress treated inputs in wrong order; closes #2495

The previous behavior when setting a field after indexing to
select an element was suitable for the hard mask case, but
not for the default soft mask.  In addition, the _hardmask
value was not being set at all in the mvoid instance.  With
this changeset, the _hardmask is passed in and __setitem__
takes it into account.