Have testLoadTkFailure() skip on cygwin since Tcl/Tk on cygwin renders to the Windows GDI directly and thus does not need a DISPLAY environment variable.
Have testLoadTkFailure() skip on cygwin since Tcl/Tk on cygwin renders to the
Windows GDI directly and thus does not need a DISPLAY environment variable.

Thanks Jason Tishler.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator