Fixes the errors with use of asyncio in docrepr/tests/test_output.py:
     
>       await compare_screenshots(test_id, url)
E       TypeError: 'coroutine' object is not callable

--- a/conftest.py
+++ b/conftest.py
@@ -65,7 +65,7 @@ def _open_browser(url):
 
 
 @pytest.fixture
-async def compare_screenshots(request):
+def compare_screenshots(request):
     """Run visual regression test on the output."""
     async def _compare_screenshots(test_id, url):
         if (request.config.getoption(COMPARE_SCREENSHOTS_OPTION) or
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<tr><td><span title='2019-06-10 23:11:07 +0200'>2019-06-10</span></td><td><a href='/guix/commit/gnu/artwork.scm?id=226a3605d6cabeb71247a732a99d625c9cfafa74'>artwork: Update snapshot to 2f2fe74.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/artwork.scm (%artwork-repository): Update to 2f2fe74.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Diego Nicola Barbato</td></tr>
<tr><td><span title='2019-03-05 23:08:53 +0100'>2019-03-05</span></td><td><a href='/guix/commit/gnu/artwork.scm?id=5387971a9ecf511e1dbbac992af3808437e58d56'>artwork: Update snapshot to b975164.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/artwork.scm (%artwork-repository): Update to b975164.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-02-10 23:25:01 +0100'>2019-02-10</span></td><td><a href='/guix/commit/gnu/artwork.scm?id=5e6a5aeebd7b735e5d5f2eed496cc1c7e8a5b4c9'>artwork: Update snapshot to e951905.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/artwork.scm (%artwork-repository): Update to e951905.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-11-05 00:08:47 +0100'>2018-11-05</span></td><td><a href='/guix/commit/gnu/artwork.scm?id=688d1a01e45eb1277a6337987bfd53f3fe3caaec'>artwork: Clone over HTTPS.</a><span class='msg-avail'>...<span class='msg-tooltip'>Suggested by Leo Famulari &lt;leo@famulari.name&gt;
at &lt;https://lists.gnu.org/archive/html/help-guix/2018-11/msg00039.html&gt;.

* gnu/artwork.scm (%artwork-repository): Switch to HTTPS URL.
</span></span></td><td>Ludovic Courtès</td></tr>