--- a/dom/media/test/external/external_media_tests/media_utils/video_puppeteer.py
+++ b/dom/media/test/external/external_media_tests/media_utils/video_puppeteer.py
@@ -400,19 +400,20 @@ class VideoPuppeteer(object):
             '\t(video)'
         ]
         messages += ['\tinterval: {}'.format(self.interval)]
         messages += ['\texpected duration: {}'.format(self.expected_duration)]
         messages += ['\tstall wait time: {}'.format(self.stall_wait_time)]
         messages += ['\ttimeout: {}'.format(self.timeout)]
         # Print each field on its own line
         for field in self._last_seen_video_state._fields:
-            messages += [('\t{}: {}'
-                          .format(field, getattr(self._last_seen_video_state,
-                                                 field)))]
+            # For compatibility with different test environments we force ascii
+            field_ascii = (str(getattr(self._last_seen_video_state, field))
+                           .encode('ascii','replace'))
+            messages += [('\t{}: {}'.format(field, field_ascii))]
         messages += '}'
         return '\n'.join(messages)
 
 
 class VideoException(Exception):
     """
     Exception class to use for video-specific error processing.
     """

--- a/dom/media/test/external/external_media_tests/media_utils/youtube_puppeteer.py
+++ b/dom/media/test/external/external_media_tests/media_utils/youtube_puppeteer.py
@@ -479,13 +479,14 @@ class YouTubePuppeteer(VideoPuppeteer):
         if not self.player:
             messages += ['\t.html5-media-player: None']
             return '\n'.join(messages)
         if not self._last_seen_player_state:
             messages += ['\t.html5-media-player: No last seen state']
             return '\n'.join(messages)
         messages += ['.html5-media-player: {']
         for field in self._last_seen_player_state._fields:
-            messages += [('\t{}: {}'
-                          .format(field, getattr(self._last_seen_player_state,
-                                                 field)))]
+            # For compatibility with different test environments we force ascii
+            field_ascii = (str(getattr(self._last_seen_video_state, field))
+                           .encode('ascii', 'replace'))
+            messages += [('\t{}: {}'.format(field, field_ascii))]
         messages += '}'
         return '\n'.join(messages)