[gegl] (5 commits) Non-fast-forward update to branch wip/Jehan/gegl_node_process_success

[Jehan <jehanp src gnome org>]

The branch 'wip/Jehan/gegl_node_process_success' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  bdf961f... gegl, operations, tests: allow running gegl_operation_set_e
  2b4e22e... operations: propagate ffmpeg errors to GEGL.
  1016ccc... tests: improve the test-errors output.
  de49b2d... tests: improve unit tests for testing gegl_node_process_suc

Commits added to the branch:

  5cd3c97... gegl, operations, tests: allow running gegl_operation_set_e
  7cc91e0... operations: propagate ffmpeg errors to GEGL.
  74b0eb1... tests: improve the test-errors output.
  10c52de... tests: improve unit tests for testing gegl_node_process_suc
  250de5c... operations: propagate libpng errors into GError.