[FIX] tools: fix guess_mimetype coming from libmagic

Since 5a9e1af6 our guess_mimetype accepted a `default` named argument.

This commit fix the use of library used instead of our implementation, so
we don't get an error from an unexpected argument when having python-magic
installed on a given server.

Since python-magic functions always return a default mimetype:

- empty content: application/x-empty
- text content: text/plain
- binary content: application/octet-stream

the guess_mimetype default argument is not used with python-magic
implementations.

closes #13343
opw-687354

openerp/addons/base/tests/test_mimetypes.py

@@ -21,11 +21,18 @@ class test_guess_mimetype(unittest.TestCase):
 
     def test_default_mimetype_empty(self):
         mimetype = guess_mimetype('')
-        self.assertEqual(mimetype, 'application/octet-stream')
+        # odoo implementation returns application/octet-stream by default
+        # if available, python-magic returns application/x-empty
+        self.assertIn(mimetype, ('application/octet-stream', 'application/x-empty'))
 
     def test_default_mimetype(self):
         mimetype = guess_mimetype('', default='test')
-        self.assertEqual(mimetype, 'test')
+        # if available, python-magic returns application/x-empty
+        self.assertIn(mimetype, ('test', 'application/x-empty'))
+
+    def test_mimetype_octet_stream(self):
+        mimetype = guess_mimetype('\0')
+        self.assertEqual(mimetype, 'application/octet-stream')
 
     def test_mimetype_png(self):
         content = base64.b64decode(PNG)
@@ -35,7 +42,8 @@ class test_guess_mimetype(unittest.TestCase):
     def test_mimetype_bmp(self):
         content = base64.b64decode(BMP)
         mimetype = guess_mimetype(content, default='test')
-        self.assertEqual(mimetype, 'image/bmp')
+        # mimetype should match image/bmp, image/x-ms-bmp, ...
+        self.assertRegexpMatches(mimetype, r'image/.*\bbmp')
 
     def test_mimetype_jpg(self):
         content = base64.b64decode(JPG)

openerp/tools/mimetypes.py

@@ -153,9 +153,9 @@ else:
 
     # magic from pypi https://pypi.python.org/pypi/python-magic/
     if hasattr(magic,'from_buffer'):
-        guess_mimetype = lambda bin_data: magic.from_buffer(bin_data, mime=True)
+        guess_mimetype = lambda bin_data, default=None: magic.from_buffer(bin_data, mime=True)
     # magic from file(1) https://packages.debian.org/squeeze/python-magic
     elif hasattr(magic,'open'):
         ms = magic.open(magic.MAGIC_MIME_TYPE)
         ms.load()
-        guess_mimetype = ms.buffer
+        guess_mimetype = lambda bin_data, default=None: ms.buffer(bin_data)