exclude another incomatible read-write-mode-combination

diff --git a/testing/test_volume_split.py b/testing/test_volume_split.py
index 41ac57a..620dd06 100755 (executable)
--- a/testing/test_volume_split.py
+++ b/testing/test_volume_split.py
@@ -335,6 +335,9 @@ def test_forever():
                         # figure out extract mode for tar file
                         if ('#' in extract_start) and ('#' not in create_mode):
                             continue    # not possible
+                        if ':' in extract_start and \
+                                not create_mode.endswith('tar'):
+                            continue    # not possible
                         full_extract_mode = extract_start
                         if extract_start[-1] != '*':
                             full_extract_mode += create_mode[2:]