Flaky TestReadPairs.test_filter_inward test

[Apteryks]

Hi,

I've recently encountered the following failure while building the python-fanc package in the Guix CI:

=================================== FAILURES ===================================
_______________________ TestReadPairs.test_filter_inward _______________________

self = <test_pairs.TestReadPairs object at 0x7fff0beae4f0>

    def test_filter_inward(self):
        mask = self.pairs.add_mask_description('inwards', 'Mask read pairs that are inward '
                                                          'facing and closer than 100bp')
        in_filter = InwardPairsFilter(minimum_distance=100, mask=mask)
    
>       assert len(self.pairs) == 44
E       assert 0 == 44
E         +0
E         -44

fanc/test/test_pairs.py:115: AssertionError
---------------------------- Captured stderr setup -----------------------------
Mappability 100% (0 of N/A) |#           | Elapsed Time: 0:00:00 ETA:  --:--:--
Mappability 100% (0 of N/A) |#           | Elapsed Time: 0:00:00 ETA:  --:--:--

The full build log is available at https://ci.guix.gnu.org/build/672406/log/raw.