QFileDialog.getSaveFileName and getOpenFileName return tuple not str

[sparkalive]

getSaveFileName and getOpenFileName returns a tuple(file path and selected filter) in Qt5 and Qt.py, but rez gui is expecting the return value is a string.

Example errors:

Traceback (most recent call last):
  File "rezgui/windows/ContextSubWindow.py", line 101, in save_context_as
    self._save_context_as()
  File "rezgui/windows/ContextSubWindow.py", line 134, in _save_context_as
    self.context_model.save(filepath)
  File "rezgui/models/ContextModel.py", line 151, in save
    self._context.save(filepath)
  File "rez/resolved_context.py", line 541, in save
    with open(path, 'w') as f:
IOError: [Errno 2] No such file or directory: "(u'maya-2018', u'Context files (*.rxt)')"