Issue #15168: Move importlb.test to test.test_importlib.

This should make the Linux distros happy as it is now easier to leave
importlib's tests out of their base Python distribution.

Lib/test/test_importlib/__init__.py

@@ -0,0 +1,33 @@
+import os
+import sys
+from .. import support
+import unittest
+
+def test_suite(package=__package__, directory=os.path.dirname(__file__)):
+    suite = unittest.TestSuite()
+    for name in os.listdir(directory):
+        if name.startswith(('.', '__')):
+            continue
+        path = os.path.join(directory, name)
+        if (os.path.isfile(path) and name.startswith('test_') and
+                name.endswith('.py')):
+            submodule_name = os.path.splitext(name)[0]
+            module_name = "{0}.{1}".format(package, submodule_name)
+            __import__(module_name, level=0)
+            module_tests = unittest.findTestCases(sys.modules[module_name])
+            suite.addTest(module_tests)
+        elif os.path.isdir(path):
+            package_name = "{0}.{1}".format(package, name)
+            __import__(package_name, level=0)
+            package_tests = getattr(sys.modules[package_name], 'test_suite')()
+            suite.addTest(package_tests)
+        else:
+            continue
+    return suite
+
+
+def test_main():
+    start_dir = os.path.dirname(__file__)
+    top_dir = os.path.dirname(os.path.dirname(start_dir))
+    test_loader = unittest.TestLoader()
+    support.run_unittest(test_loader.discover(start_dir, top_level_dir=top_dir))