Consider killing --rcfile option.

[jsirois]

The option only works at build-time and presents awkward semantic choices wrt PEX_IGNORE_RCFILES. Investigate why this option was added and kill it if the justification is weak or no longer pertinent.

[jsirois]

Ok, added in #427 and, just like the option help says, really only to support a few integration tests. I'm pretty sure the flag can die and the integration tests be made to work in other ways.

[jsirois]

@CMLivingston perhaps this is a better place to comment on the --rcfile awkwardness. Would you agree the option can die if the integration test can be made to work in other ways?

[CMLivingston]

Absolutely, I agree that is is a weird interface.

[jsirois]

This cannot happen until Pex 3, if ever. I'll leave open but just note Pex has been firmly of the stance it does not break backward compatibility for a while now.