test cases fail for pyqt5

[Joern Ungermann]

Test for trajectory tool fail for pyt5 whereas they complete for pyqt4. Also py.test crashes instead of providing a reason for the fail.

[Reimar Bauer]

Add tuple handler to filename open dialog like in other places

to make mocking of testcase work in pyqt5

Fix issue #310

→ <<cset ce7c8623824f>>