Make recursive pdb properly invoke IPython's enhanced pdb

[segevfiner]

The problem is that Pdb.do_debug creates a new instance of the original Pdb rather than our derived Pdb/TerminalPdb. So I copied Lib/pdb.py:1087-1102 and made it use our own class instead.

I had to:

1. Switch to keyword arguments because IPython changes Pdb's init signature.
2. Add a line to propagate use_rawinput. Without that the propagation of stdout triggers use_rawinput = 0, breaking TerminalPdb. This is probably a bug in Python, see: bpo-31078.

For IPython 5, the self.message lines need to be changed to a print. See Lib/pdb.py:712-722 (2.7).

• Do we want to change the nested Pdb's prompt calculation? Now it uses (ipdb>) , adding more parentheses to each nesting level (Pdb's default prompt is (Pdb) ).

Fixes #1273

[takluyver]

Thanks! I've milestoned it for 6.2 as a new feature, so the self.message() statements should be fine.

Like Fernando back in 2012, I had no idea that recursive pdb was a thing, so whatever you think makes sense for the prompt is fine by me!

[Carreau]

@segevfiner is that good as is ? I'm happy to get it into 6.2, or do you want to add extra things like the prompt ?

[segevfiner]

The prompt is a matter of taste. pdb's prompt is (Pdb) and when you invoke it recursively, it changes into ((Pdb)) with more parentheses added for each level of recursion. ipdb uses ipdb> and since I left that calculation as is, it will use (ipdb>) when invoked recursively. Unless you prefer some other prompt for the recursive invocation, than this PR is ready.

[Carreau]

The prompt is a matter of taste. pdb's prompt is (Pdb) and when you invoke it recursively, it changes into ((Pdb)) with more parentheses added for each level of recursion. ipdb uses ipdb> and since I left that calculation as is, it will use (ipdb>) when invoked recursively. Unless you prefer some other prompt for the recursive invocation, than this PR is ready.

ok, perfect, thank you, sorry for the delay them from the overview in the PR list there was a "0 out of 1", and though you wanted to add something.

Merging.