The update_wc_on_windows_drive test requires the Python for Windows Extensions to be installed. Skip the test if they aren't.
The update_wc_on_windows_drive test requires the Python for Windows Extensions
to be installed. Skip the test if they aren't.

* subversion/tests/cmdline/update_tests.py
  (find_the_next_available_drive_letter): return no available drive when the 
   win32api module can't be loaded.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@861608 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion