Python repl should support tab complete

[JettJones]

Is your feature request related to a problem? Please describe.
Current versions of python 3.x support tab complete when run directly (https://docs.python.org/3/tutorial/interactive.html), it would be nice if this was also available in pants repl ....

Describe the solution you'd like
Matching behavior of python started directly / in interactive -i mode.

>>> x = []
>>> x.  # then tab generates:
x.append(   x.clear(    x.copy(     x.count(    x.extend(   x.index(    x.insert(   x.pop(      x.remove(   x.reverse(  x.sort(
>>> import sys
>>> sys.  # then tab generates:
sys.abiflags                              sys.getallocatedblocks(                   sys.path_hooks
sys.addaudithook(                         sys.getdefaultencoding(                   sys.path_importer_cache
sys.api_version                           sys.getdlopenflags(                       sys.platform
sys.argv                                  sys.getfilesystemencodeerrors(            sys.platlibdir
...

Describe alternatives you've considered
Running with --shell=ipython activates the autocomplete in ipython, but it's a slightly different interface, so one more thing to learn.

Additional context

[benjyw]

Supporting this is a good idea. Would be great if you could do some further debugging here to see in what way the Pants repl is different from a standalone one, and why this might cause tab completion to be disabled.

[jsirois]

The underlying problem is in Pex and is being addressed here: pex-tool/pex#2321

Once Pex 2.1.158 is released with the fix, a Pants maintainer will need to upgrade the Pex version Pants uses / provide you with instructions on how to self-upgrade your existing Pants install using pants.toml config.

[jsirois]

Ok, Pex 2.1.158 is released: https://github.com/pantsbuild/pex/releases/tag/v2.1.158

[benjyw]

Thanks @jsirois !

@JettJones You can upgrade in your own repo by setting version and known_versions under [pex-cli] in your pants.toml, as described here.

If that works, we'd appreciate a PR that changes the default version of Pex that Pants uses, which is set here.

[JettJones]

cburroughs patch works for me! Thanks for jumping on that.