tests/fpcmoc: Ensure python tests exit with error on every exception

We ignored assertions happening on callbacks as they only raise
exceptions that does not stop the execution.

So ensure that this is happening in all the tests as synaptics was
doing already

Same as commit: be8888431

tests/fpcmoc/custom.py

@@ -1,9 +1,15 @@
 #!/usr/bin/python3
 
+import traceback
+import sys
 import gi
+
 gi.require_version('FPrint', '2.0')
 from gi.repository import FPrint, GLib
 
+# Exit with error on any exception, included those happening in async callbacks
+sys.excepthook = lambda *args: (traceback.print_exception(*args), sys.exit(1))
+
 ctx = GLib.main_context_default()
 
 c = FPrint.Context()