py-pyzstd: tests fail from clean state because glob is used in global part of portfile

[ryandesign (Ryan Carsten Schmidt)]

py-pyzstd does:

    test.env        PYTHONPATH=[glob -nocomplain ${worksrcpath}/build/lib*]

This won't work if the port is in a clean state at the time the portfile is parsed because ${worksrcpath} and its contents don't exist yet.

For example: sudo port clean py39-pyzstd && sudo port test py39-pyzstd fails because PYTHONPATH is empty:

:debug:test Environment:

:debug:test PYTHONPATH=''

:info:test test_zstd (unittest.loader._FailedTest) ... ERROR
:info:test ======================================================================
:info:test ERROR: test_zstd (unittest.loader._FailedTest)
:info:test ----------------------------------------------------------------------
:info:test ImportError: Failed to import test module: test_zstd
:info:test Traceback (most recent call last):
:info:test   File "/opt/local/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/unittest/loader.py", line 154, in loadTestsFromName
:info:test     module = __import__(module_name)
:info:test   File "/opt/local/var/macports/build/_Users_rschmidt_macports_macports-ports-ryandesign-fork_python_py-pyzstd/py39-pyzstd/work/pyzstd-0.15.0/tests/test_zstd.py", line 20, in <module>
:info:test     import pyzstd
:info:test ModuleNotFoundError: No module named 'pyzstd'
:info:test ----------------------------------------------------------------------

A subsequent sudo port test py39-pyzstd without cleaning first succeeds.

To avoid this problem, if you need to glob or otherwise inspect the contents of ${worksrcpath}, you can't do it in the global part of the portfile. You have to defer it to a time when ${worksrcpath} exists. In this case, you should enclose at least the test.env line in a pre-test block.