Enable debug output at the start of the regression suite instead.

Sorry for the ephemeral inconvenience.

Lib/test/regrtest.py

@@ -450,6 +450,9 @@ def main(tests=None, testdir=None, verbose=0, quiet=False,
         print("==  ", platform.platform(aliased=True),
                       "%s-endian" % sys.byteorder)
         print("==  ", os.getcwd())
+        import pprint, errno
+        print("== Errno map:")
+        pprint.pprint(errno.errorcode)
 
     alltests = findtests(testdir, stdtests, nottests)
     selected = tests or args or alltests