The Clar test framework has a bug whereby it skips the parsing phase
on files with mtime=0.

Reported upstream at <https://github.com/vmg/clar/pull/78>.

diff --git a/tests/generate.py b/tests/generate.py
index b639c8f..111ca41 100644
--- a/tests/generate.py
+++ b/tests/generate.py
@@ -63,3 +63,3 @@ class Module(object):
 
-        self.mtime = 0
+        self.mtime = None # Guix sets all file mtimes to '0'
         self.enabled = True
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<tr><td><span title='2021-05-20 01:58:04 +0200'>2021-05-20</span></td><td><a href='/guix/commit/README?id=c0087d33705f53cc3619a1a43a33602aaecc3a8b'>The #guix channel is hosted by Libera Chat.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
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