bpo-34022: Unbreak importlib tests when SOURCE_DATE_EPOCH is set

[elprans]

SOURCE_DATE_EPOCH forces py_compile to use the CHECKED_HASH .pyc
invalidation mode, and some tests fail when it is enabled.

The solution is to unset SOURCE_DATE_EPOCH for tests that expect a
different invalidation mode. This also makes all relevant tests run
with SOURCE_DATE_EPOCH set explicitly.

https://bugs.python.org/issue34022

[mcepl]

Wouldn't it better to go in the other direction: to make tests where it matters check for the existence of the environmental variable and modify their expectations accordingly?

[elprans]

No. These are tests for specific invalidation behavior. Skipping or otherwise modifying the tests would lead to gaps in coverage. And SOURCE_DATE_EPOCH itself is tested elsewhere in test_py_compile.

[thehesiod]

with this patch I'm still getting the following errors when we build 3.7.0

======================================================================
FAIL: test_force (test.test_compileall.CommandLineTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 365, in test_force
self.assertEqual(mtime, mtime2)
AssertionError: 1538001451.0582225 != 1538001511.103473
======================================================================
FAIL: test_no_args_respects_force_flag (test.test_compileall.CommandLineTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 299, in test_no_args_respects_force_flag
self.assertEqual(mtime, mtime2)
AssertionError: 1538001451.8885925 != 1538001511.943473
======================================================================
FAIL: test_pyc_invalidation_mode (test.test_compileall.CommandLineTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 533, in test_pyc_invalidation_mode
self.assertEqual(int.from_bytes(data[4:8], 'little'), 0b01)
AssertionError: 3 != 1
======================================================================
FAIL: test_magic_number (test.test_compileall.CompileallTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 78, in test_magic_number
self.recreation_check(b'\0\0\0\0')
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 61, in recreation_check
self.assertEqual(*self.data())
AssertionError: b'B\r\r\n\x03\x00\x00\x00\\s\xa0J' != b'B\r\r\n\x00\x00\x00\x00i\n\xac['
======================================================================
FAIL: test_mtime (test.test_compileall.CompileallTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 74, in test_mtime
0, 1))
File "/build/Python-3.7.0/Lib/test/test_compileall.py", line 61, in recreation_check
self.assertEqual(*self.data())
AssertionError: b'B\r\r\n\x03\x00\x00\x00\\s\xa0J' != b'B\r\r\n\x00\x00\x00\x00i\n\xac['
----------------------------------------------------------------------

reverting ccbe5818af2 does fix it. In particular for me I'm compiling 3.7.0 via dpkg-buildpackage -b -nc -us -uc -rfakeroot -jauto which I'm guessing somewhere sets SOURCE_DATE_EPOCH

[elprans]

Yes, I think that ccbe581 is broken. I'll submit another PR with a proposed fix.

[elprans]

Closing in favor of #9607.