RT02 enforces the pandas docstring guide, not the numpydoc docstring guide

The RT02 error has the description:

"The first line of the Returns section should contain only the type, unless multiple values are being returned"

This appears to enforce the pandas docstring guide:

"...no name will be provided, unless the method returns or yields more than one value"

In contrast, the numpydoc docstring guide states:

"...the name of each return value is optional. The type of each return value is always required"

This is a concern for SciPy, where the general standard has been to specify the name of all return values, even when only a single value is returned. As a very rough measure, over 42% of the functions in scipy.stats are currently tripping RT02 errors (and that's without bothering to bracket out the functions which return multiple values).

Possible solutions:

1. Update the numpydoc docstring guide to stipulate what RT02 enforces. This would necessitate a lot of little edits (at least for SciPy) and the loss of some potentially valuable information from the documentation.

2. Remove RT02 from numpydoc.validate. But then, pandas either loses that particular validation or has to (re)implement a version of the script in their project, which would be a reversal of the recent effort to bring things from pandas to numpydoc.

3. Or, as a compromise, demote RT02 to a warning, which would only report if specifically requested. If numpydoc doesn't mind maintaining non-numpydoc warnings, a central collection would be convenient for numpydoc users looking for stricter validation. Further, if there is a desire to update the numpydoc docstring guide, collaborating about such warnings would be a great place to start.

Start with RT02 in numpydoc/validate.py and read the linked numpydoc and pandas guidance. Review the three proposed resolutions and the existing discussion before choosing a project decision; done means the validator behavior and documented standard agree, with any selected warning behavior applied consistently.