Provide an interface consistent with pdb so that pudb can be used by pytest

[anntzer]

pytest provides the switch --pdb in order to enter a debugger whenever a test fails. In pytest-dev/pytest#1712 I added the --pdbcls flag to pytest so that one can specify an arbitrary Pdb subclass; e.g. one can call py.test --pdbcls=IPython.core.debugger:Pdb --pdb to use the ipython debugger instead.

Unfortunately it is currently not possible to pass in pudb (py.test --pdbcls=pudb.debugger:Debugger --pdb) because the Debugger.interaction method has a completely different signature than Pdb.interaction (which is the entry point used), leading to a crash of pytest. Specifically, the signatures are

pdb.Pdb.interaction(self, frame, traceback)

and

pudb.debugger.Debugger.interaction(self, frame, exc_tuple=None, show_exc_dialog=True)

Would it be possible to modify the signature of Debugger.interaction so that the second argument becomes, say, exc_tuple_or_traceback (to maintain backcompatibility and also be compatible with pytest)?

[asmeurer]

It sounds good to me. Have you tested it to see if there are any other compatibility issues that pop up?

[anntzer]

Well, I haven't implemented anything and am not so familiar with pudb's internals so I can't tell.

[inducer]

Likewise, sounds good to me. Try it out and send a PR if it turns out to work.

[anntzer]

Closed by #224, IIRC.