Issue #23839: Various caches now are cleared before running every test file.

diff --cc Misc/NEWS
index 31c3703b546655fb32524e3d6f19f531a2af5119,15f5725955281a953eb2327d596cb70ac240ae92..0d4e72da3a113b6a959e5048e930cdbf6be79b6b
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -443,11 -457,6 +443,13 @@@ Tools/Demo
  Tests
  -----
  
++- Issue #23839: Various caches now are cleared before running every test file.
++
 +- Issue #26944: Fix test_posix for Android where 'id -G' is entirely wrong or
 +  missing the effective gid.
 +
 +- Issue #28409: regrtest: fix the parser of command line arguments.
 +
  - Issue #28217: Adds _testconsole module to test console input.