Update test to check specific contents of squashfs listing, otherwise it fails...

Update test to check specific contents of squashfs listing, otherwise it fails depending on the test systems uid to username passwd(5) mapping.

tests/comparators/test_squashfs.py

@@ -22,7 +22,7 @@ import subprocess
 
 from diffoscope.comparators.squashfs import SquashfsFile
 
-from ..utils.data import load_fixture, assert_diff
+from ..utils.data import load_fixture, assert_diff, get_data
 from ..utils.tools import skip_unless_tools_exist, skip_unless_tool_is_at_least
 from ..utils.nonexisting import assert_non_existing
 
@@ -97,4 +97,7 @@ def differences_root(squashfs1_root, squashfs2_root):
 
 @skip_unless_tools_exist("unsquashfs")
 def test_symlink_root(differences_root):
-    assert_diff(differences_root[1], "squashfs_root_expected_diff")
+    assert (
+        get_data("squashfs_root_expected_diff")
+        in differences_root[1].unified_diff
+    )

tests/data/squashfs_root_expected_diff

-@@ -1,7 +1,7 @@
- Parallel unsquashfs: Using 8 processors
- 3 inodes (3 blocks) to write
- 
--drwxr-xr-x lamby/lamby              51 2015-06-24 14:47 
--lrwxrwxrwx lamby/lamby               6 2015-06-24 14:47 /link -> broken
-+drwxr-xr-x lamby/lamby              51 2015-06-24 14:50 
-+lrwxrwxrwx lamby/lamby              13 2015-06-24 14:50 /link -> really-broken
  crw-r--r-- root/root             1,  3 2015-06-24 14:47 /null
---rw-r--r-- lamby/lamby             446 2015-06-24 14:49 /text
-+-rw-r--r-- lamby/lamby             671 2015-06-24 14:49 /text