More to this issue: if you run openstack_dashboard py27dj19 tests, a lot of tests (or all of them?) produce this kind of noise:

Traceback (most recent call last):
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/loader_tags.py", line 209, in render
    return template.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 208, in render
    return self._render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/test/utils.py", line 92, in instrumented_test_render
    return self.nodelist.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 988, in render
    bit = node.render_annotated(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 955, in render_annotated
    return self.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/templatetags/compress.py", line 127, in render
    return self.render_compressed(context, self.kind, self.mode, forced=forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/templatetags/compress.py", line 103, in render_compressed
    rendered_output = compressor.output(mode, forced=forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/css.py", line 49, in output
    ret.append(subnode.output(*args, **kwargs))
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/css.py", line 51, in output
    return super(CssCompressor, self).output(*args, **kwargs)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 299, in output
    return self.handle_output(mode, filtered_output, forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 307, in handle_output
    return output_func(mode, content, forced, basename)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 321, in output_file
    return self.render_output(mode, {"url": url})
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 350, in render_output
    mode=mode, context=final_context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 192, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/home/tsufiev/develop/horizon/horizon/templatetags/angular.py", line 36, in update_angular_template_hash
    theme = context['THEME']  # current theme being compressed
KeyError: 'THEME'
WARNING:django.template:Exception raised while rendering {% include %} for template 'admin/flavors/create.html'. Empty string rendered instead.
Traceback (most recent call last):
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/loader_tags.py", line 209, in render
    return template.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 208, in render
    return self._render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/test/utils.py", line 92, in instrumented_test_render
    return self.nodelist.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 988, in render
    bit = node.render_annotated(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/template/base.py", line 955, in render_annotated
    return self.render(context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/templatetags/compress.py", line 127, in render
    return self.render_compressed(context, self.kind, self.mode, forced=forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/templatetags/compress.py", line 103, in render_compressed
    rendered_output = compressor.output(mode, forced=forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/js.py", line 50, in output
    ret.append(subnode.output(*args, **kwargs))
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/js.py", line 52, in output
    return super(JsCompressor, self).output(*args, **kwargs)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 299, in output
    return self.handle_output(mode, filtered_output, forced)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 307, in handle_output
    return output_func(mode, content, forced, basename)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 321, in output_file
    return self.render_output(mode, {"url": url})
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/compressor/base.py", line 350, in render_output
    mode=mode, context=final_context)
  File "/home/tsufiev/develop/horizon/.venv/local/lib/python2.7/site-packages/django/dispatch/dispatcher.py", line 192, in send
    response = receiver(signal=self, sender=sender, **named)
  File "/home/tsufiev/develop/horizon/horizon/templatetags/angular.py", line 36, in update_angular_template_hash
    theme = context['THEME']  # current theme being compressed
KeyError: 'THEME'

I called it a noise, because these tests still succeed. Yet it is quite distracting.