turn RecordedWarning into a namedtuple

[RonnyPfannschmidt]

fixes #2013

[coveralls]

Coverage decreased (-0.005%) to 92.844% when pulling ce66923 on RonnyPfannschmidt:warning-record-namedtuple into c0719a5 on pytest-dev:master.

[nicoddemus]

LGTM other than a CHANGELOG message.

Please be descriptive of the change, specially that RecordedWarning is now a namedtuple so if someone gets tripped by it at least there's a clear warning, something like:

• RecordedWarning objects (returned by pytest.warns and recwarn fixture) are now namedtuples so they have a better default string representation when displayed in assertion messages (#number).

[nicoddemus]

There's a small side effect here, RecordedWarning attributes are now read-only.

The docs themselves have this to say about it:

Each recorded warning has the attributes message, category, filename, lineno, file, and line. The category is the class of the warning. The message is the warning itself; calling str(message) will return the actual message of the warning.

IMO your change is good and I doubt there are people writing to the attributes, but I thought I would mention this anyway.

[RonnyPfannschmidt]

Good catch, this also means this should go to features

[nicoddemus]

If you feel this way, perhaps you should just add a __repr__ method then? This would solve the issue and could go into master.

[RonnyPfannschmidt]

nope, i just reduced the amount of boilerplate to maintain, i wont add it back to add even more

[nicoddemus]

OK, no problem

[nicoddemus]

Sorry for not merging earlier, completely missed the new commits!