bug#19755: python.el: native completion: more problems (and solutions)

[Carlos Pita]

Ok, after a conversation with Fabian I understood which are the
shortcomings of the legacy mechanism:

1) While inside a block of code asking a completion to the shell makes
it believe that you're not inside the block anymore.

2) Spurious prompt number increments take place each time a completion
is requested to the shell.

So it's not just a matter of the completer being the preinstalled by
the shell or some other one that python.el instantiates itself during
the setup phase.

Another solution could be to open a simple python helper thread that
listens on a socket. This thread could provide documentation for eldoc
or for help buffers (I'm about to post a RFE for this feature),
besides the completions. Another adventage is that it will be possible
to unify the completion mechanisms again.

What do you think?

Cheers
--
Carlos