Pex

A hotfix that fixes a bug present since 2.1.25 that results in infinite
recursion in PEX runtime resolves when handling dependency cycles.

* Guard against cyclic dependency graphs. (1317)

A hotfix that finishes work started in 2.1.37 by 1304 to align Pip
based resolve results with `--pex-repository` based resolve results for
requirements with '.' in their names as allowed by PEP-503.

* Fix PEX direct requirements metadata. (1312)

* Fix Pex isolation to avoid temporary pyc files. (1308)
* Fix `--pex-repository` requirement canonicalization. (1304)
* Spruce up `pex` and `pex-tools` CLIs with uniform `-V` / `--version`
support and default value display in help. (1301)

This release brings a fix for building sdists with certain macOS
interpreters when creating a PEX file that would then fail to resolve on
PEX startup.

* Add support for `--seed verbose`. (1299)
* Fix bytecode compilation race in PEXBuilder.build. (1298)
* Fix wheel building for certain macOS system interpreters. (1296)

This release hardens a few aspects of `--venv` mode PEXes.
An infinite re-exec loop in venv `pex` scripts is fixed and
the `activate` family of scripts in the venv is fixed.

* Improve resolve error information. (1287)
* Ensure venv pex does not enter a re-exec loop. (1286)
* Expose Pex tools via a pex-tools console script. (1279)
* Fix auto-created `--venv` core scripts. (1278)

Beyond bugfixes for a few important edge cases, this release includes
new support for argfiles on the command line from jjhelmus. These
can be useful to overcome command line length limitations. See:
<https://docs.python.org/3/library/argparse.html#fromfile-prefix-chars>.

* Allow cli arguments to be specified in a file (1273)
* Fix module entrypoints. (1274)
* Guard against concurrent re-imports. (1270)
* Ensure Pip logs to stderr. (1268)