[pitivi] check: Present a human-readable error when gst-python is not working properly

[Jean-François Fortin Tam <jfft src gnome org>]

commit d1ea9a9712cad86abece03963bde9bea4564bbda
Author: Jean-François Fortin Tam <nekohayo gmail com>
Date:   Sat Nov 1 22:17:48 2014 -0400

    check: Present a human-readable error when gst-python is not working properly
    
    This is 1000x better than the cryptic traceback users get when pygst is missing

 pitivi/check.py |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)
---
diff --git a/pitivi/check.py b/pitivi/check.py
index e70446b..c2a82fb 100644
--- a/pitivi/check.py
+++ b/pitivi/check.py
@@ -212,7 +212,6 @@ SOFT_DEPENDENCIES = (PYCANBERRA_SOFT_DEPENDENCY,
 
 def _check_audiosinks():
     from gi.repository import Gst
-
     # Yes, this can still fail, if PulseAudio is non-responsive for example.
     sink = Gst.ElementFactory.make("autoaudiosink", None)
     if not sink:
@@ -220,6 +219,15 @@ def _check_audiosinks():
     return True
 
 
+def _check_gst_python():
+    from gi.repository import Gst
+    try:
+        Gst.Fraction(9001, 1)  # It's over NINE THOUSANDS!
+    except TypeError:
+        return False  # What, nine thousands?! There's no way that can be right
+    return True
+
+
 def check_requirements():
     hard_dependencies_satisfied = True
     for dependency in HARD_DEPENDENCIES:
@@ -241,6 +249,11 @@ def check_requirements():
     if not hard_dependencies_satisfied:
         return False
 
+    if not _check_gst_python():
+        print((_("ERROR — Could not create a Gst.Fraction — "
+              "this means gst-python is not installed correctly.")))
+        return False
+
     if not _check_audiosinks():
         print((_("Could not create audio output sink. "
                 "Make sure you have a valid one (pulsesink, alsasink or osssink).")))