Test fail on big-endian (s390x)

[ptrcnull]

Example from Alpine Linux edge: https://gitlab.alpinelinux.org/ptrcnull/aports/-/jobs/783199#L149

======================================================================
FAIL: test_empty (pythongettext.tests.test_compile.TestWriter)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/builds/ptrcnull/aports/community/py3-gettext/src/python-gettext-4.0/pythongettext/tests/test_compile.py", line 30, in test_empty
    self.compare_po_mo('test_empty.po', 'test_empty.mo')
  File "/builds/ptrcnull/aports/community/py3-gettext/src/python-gettext-4.0/pythongettext/tests/test_compile.py", line 27, in compare_po_mo
    self.assertEqual(mo, po)
AssertionError: b'\xde\x12\x04\x95\x00\x00\x00\x00\x00\x00\x0[65 chars]\x00' != b'\x95\x04\x12\xde\x00\x00\x00\x00\x00\x00\x0[65 chars]\x1c'

[icemac]

@ptrcnull Thank you for writing this issue. Do you have a suggestion how to solve it?

[ptrcnull]

only partially; forcing endianness in struct.pack helps a little:

diff --git a/pythongettext/msgfmt.py b/pythongettext/msgfmt.py
index 6641b52..61c4615 100755
--- a/pythongettext/msgfmt.py
+++ b/pythongettext/msgfmt.py
@@ -150,7 +150,7 @@ class Msgfmt:
         # Even though we don't use a hashtable, we still set its offset to be
         # binary compatible with the gnu gettext format produced by:
         # msgfmt file.po --no-hash
-        output = struct.pack("Iiiiiii",
+        output = struct.pack("<Iiiiiii",
                              0x950412de,        # Magic
                              0,                 # Version
                              len(keys),         # # of entries

but that doesn't solve the issue entirely

[icemac]

Since the merge of #13 we have automatic tests for this repository, so the behavior could be explored using GitHub Actions.