fix CI after upstream changes (#1071)

Author: sappelhoff

mne_bids/tests/test_write.py

@@ -84,6 +84,7 @@
                  'Setting to None.',
     cnt_warning2='ignore:.*Could not define the number of bytes automatically.'
                  ' Defaulting to 2.',
+    cnt_warning3='ignore:.*Coordinate frame could not be inferred.*',
     no_hand='ignore:.*Not setting subject handedness.:RuntimeWarning:mne',
     no_montage=r'ignore:Not setting position of.*channel found in '
                r'montage.*:RuntimeWarning:mne',
@@ -3234,6 +3235,7 @@ def test_convert_meg_formats(dir_name, format, fname, reader, tmp_path):
     warning_str['channel_unit_changed'],
     warning_str['cnt_warning1'],
     warning_str['cnt_warning2'],
+    warning_str['cnt_warning3'],
     warning_str['no_hand'],
 )
 @testing.requires_testing_data

mne_bids/write.py

@@ -125,7 +125,7 @@ def _channels_tsv(raw, fname, overwrite=False):
         ch_type.append(map_chs[_channel_type])
         description.append(map_desc[_channel_type])
     low_cutoff, high_cutoff = (raw.info['highpass'], raw.info['lowpass'])
-    if raw._orig_units is not None:
+    if raw._orig_units:
         units = [raw._orig_units.get(ch, 'n/a') for ch in raw.ch_names]
     else:
         units = [_unit2human.get(ch_i['unit'], 'n/a')