Reduce the prevalence of None as a return value

[kurtmckee]

Supersedes #152

Changes

• AuthState.introspect_token() will no longer return None if the token is not active.

  Instead, a new exception, InactiveTokenError, will be raised.
  InactiveTokenError is a subclass of ValueError.

  Existing code that calls AuthState.introspect_token() no longer returns None, either,
  but will instead raise ValueError, a subclass of ValueError,
  or a globus_sdk.GlobusAPIError:

  • AuthState.get_authorizer_for_scope
  • AuthState.effective_identity
  • AuthState.identities

[sirosen]

Some minor tweaks to apply, but I want to hold off on approving and merging until after we do a release.

Although we're now fairly certain that this won't cause impactful changes for known AP Tools users, I think including it in the next release would not match some of the messages I've sent to other teams about what to expect out of our next two releases.

[sirosen]

Gotcha! This is why they pay me the looks at his bank balance ... does that count as "big bucks"? 😛

Suggested change

	but will instead raise ``ValueError``, a subclass of ``ValueError``,
	but will instead raise ``ValueError``,

[kurtmckee]

InactiveTokenError and InvalidTokenScopesError are subclasses of ValueError...?

[sirosen]

Right, but the text says that ValueError is a subclass of ValueError, unless I'm very confused. (And if I am, I'll count that as a request for a rephrase!)

[sirosen]

Oh! I see now. It's a list of options, of length 3,

• ValueError
• a subclass of ValueError
• globus_sdk.GlobusAPIError

I thought it was a list of length 2,

• ValueError, a subclass of ValueError
• globus_sdk.GlobusAPIError

Can we scratch "a subclass of ValueError" from the list, but now on different grounds, which is that it's unnecessary to specify?

[kurtmckee]

One last alternate:

ValueError (or a subclass) or globus_sdk.GlobusAPIError

?

[sirosen]

My approval should speak for itself.

But since it doesn't seem to speak up, "yes!" and "w00t!" and other exclamations of joy. I now understand the text and it says everything you wanted it to say!