Adding lib/test/__main__.py for running tests with 'python -m test'

Lib/test/__main__.py

+import os
+import sys
+import sysconfig
+
+from test import support
+from test import regrtest
+
+# findtestdir() gets the dirname out of __file__, so we have to make it
+# absolute before changing the working directory.
+# For example __file__ may be relative when running trace or profile.
+# See issue #9323.
+__file__ = os.path.abspath(__file__)
+
+# sanity check
+assert __file__ == os.path.abspath(sys.argv[0])
+
+# When tests are run from the Python build directory, it is best practice
+# to keep the test files in a subfolder.  It eases the cleanup of leftover
+# files using command "make distclean".
+if sysconfig.is_python_build():
+    TEMPDIR = os.path.join(sysconfig.get_config_var('srcdir'), 'build')
+    TEMPDIR = os.path.abspath(TEMPDIR)
+    if not os.path.exists(TEMPDIR):
+        os.mkdir(TEMPDIR)
+    regrtest.TEMPDIR = TEMPDIR
+
+# Define a writable temp dir that will be used as cwd while running
+# the tests. The name of the dir includes the pid to allow parallel
+# testing (see the -j option).
+TESTCWD = 'test_python_{}'.format(os.getpid())
+
+TESTCWD = os.path.join(TEMPDIR, TESTCWD)
+regrtest.TESTCWD = TESTCWD
+
+# Run the tests in a context manager that temporary changes the CWD to a
+# temporary and writable directory. If it's not possible to create or
+# change the CWD, the original CWD will be used. The original CWD is
+# available from support.SAVEDCWD.
+with support.temp_cwd(TESTCWD, quiet=True):
+    regrtest.main()