Enable most unittests on python3 (just some vault unittests and a logging one left) (#17240)

Make some python3 fixes to make the unittests pass:

* galaxy imports
* dictionary iteration in role requirements
* swap_stdout helper for unittests
* Normalize to text string in a facts.py function

test/units/module_utils/basic/test_run_command.py

@@ -42,7 +42,6 @@ class OpenBytesIO(BytesIO):
         pass
 
 
-@unittest.skipIf(sys.version_info[0] >= 3, "Python 3 is not supported on targets (yet)")
 class TestAnsibleModuleRunCommand(unittest.TestCase):
     def setUp(self):
         self.cmd_out = {