MTA mode for COM client (pywinauto#427)

* Switch on COM client MTA mode by default

* Prevent pythoncom conflicts while setting COM client in MTA mode

pywinauto/__init__.py

@@ -34,9 +34,21 @@
 
 __version__ = "0.6.3"
 
-import sys
+import sys  # noqa: E402
 
 if sys.platform == 'win32':
+    # Set up COM client MTA mode as early as possible as it affects not only
+    # the optional comtypes package we use, but pywin32.pythoncom module as well.
+    sys.coinit_flags = 0   # COINIT_MULTITHREADED = 0x0
+
+    # Also try to un-initialze pythoncom if it's already been loaded.
+    # However, importing only pythoncom can fail with the errors like:
+    #     ImportError: No system module 'pywintypes' (pywintypes27.dll)
+    # So try to facilitate pywintypes*.dll loading with implicit import of win32api
+    import win32api  # noqa: E402
+    import pythoncom  # noqa: E402
+    pythoncom.CoUninitialize()
+
     from . import findwindows
     WindowAmbiguousError = findwindows.WindowAmbiguousError
     ElementNotFoundError = findwindows.ElementNotFoundError
@@ -52,7 +64,6 @@
 
     from .application import Application, WindowSpecification
 
-
     class Desktop(object):
 
         """Simple class to call something like ``Desktop().WindowName.ControlName.method()``"""

pywinauto/sysinfo.py

@@ -30,17 +30,18 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 """Simple module for checking whether Python and Windows are 32-bit or 64-bit"""
-import os
 import sys
-import platform
-import ctypes
-import logging
+import os  # noqa: E402
+import platform  # noqa: E402
+import ctypes  # noqa: E402
+import logging  # noqa: E402
+
 
 try:
     # Disable 'INFO' logs from comtypes
     log = logging.getLogger('comtypes')
     log.setLevel('WARNING')
-    import comtypes
+    import comtypes  # noqa: E402
     UIA_support = True
 except ImportError:
     UIA_support = False

pywinauto/unittests/test_application.py

@@ -136,14 +136,16 @@ def testConnectWarning3264(self):
             return
 
         app = Application().start(self.sample_exe_inverted_bitness)
-        warnings.filterwarnings('always', category=UserWarning, append=True)
-        with warnings.catch_warnings(record=True) as w:
-            warnings.simplefilter("always")
-            Application().connect(path=self.sample_exe_inverted_bitness)
+        # Appveyor misteries...
+        self.assertEqual(app.is_process_running(), True)
+
+        with mock.patch("warnings.warn") as mockWarn:
+            Application().connect(process=app.process)
             app.kill_()
-            assert len(w) >= 1
-            assert issubclass(w[-1].category, UserWarning)
-            assert "64-bit" in str(w[-1].message)
+            args, kw = mockWarn.call_args
+            assert len(args) == 2
+            assert "64-bit" in args[0]
+            assert args[1].__name__ == 'UserWarning'
 
 
 class ApplicationTestCases(unittest.TestCase):