Fix for Python Magic API change

[StevenMaude]

Here, python-magic changed the behaviour of from_buffer().

This breaks a new install of messytables on Python 3.4, shown by tests failing:

  File ".../messytables/messytables/any.py", line 66, in get_mime
    mimetype = magic.from_buffer(header, mime=True).decode('utf-8')
AttributeError: 'str' object has no attribute 'decode'

The alternative fix would be to pin python-magic at some version <0.4.12.

[StevenMaude]

This also fixes the Travis tests, which is a separate html5lib issue (a change which can be revoked when they update PyPI, I think the fix is already merged on their GitHub).

Can separate this out into another PR if you prefer, though it meant I could demonstrate tests passing on this PR.

[frabcus]

I get lots of errors like this, in Python 2 or 3, when running nosetests on this branch.

ERROR: test.test_any.test_simple({'tableset': <class 'messytables.excel.XLSTableSet'>, 'filename': 'bian-anal-mca-2005-dols-eng-1011-0312-tab3.xlsm'},)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/nose/case.py", line 197, in runTest
    self.test(*self.arg)
  File "/home/francis/code/fiddle/messytables-steve/test/test_any.py", line 42, in check_no_filename
    table_set = any_tableset(fh)
  File "/home/francis/code/fiddle/messytables-steve/messytables/any.py", line 152, in any_tableset
    magic_mime = get_mime(fileobj)
  File "/home/francis/code/fiddle/messytables-steve/messytables/any.py", line 66, in get_mime
    mimetype = magic.from_buffer(header, mime=True)
AttributeError: 'module' object has no attribute 'from_buffer'

[StevenMaude]

@frabcus Weird. That looks like any.py can't see magic's from_buffer() at all.

Do you get the same issue running nosetests on master locally, or just on my branch?

Also worth checking if

python -c "from __future__ import print_function; import magic; print(magic.from_buffer)"

gives you an error.

[StevenMaude]

@frabcus: long shot, you don't by any chance have filemagic installed and it's shadowing python-magic? (pip freeze should tell you.)

It uses the same module name, magic. When I installed this in my virtualenv containing python-magic, I got the AttributeError as above. After uninstalling filemagic, accessing from_buffer worked again.

[StevenMaude]

The output of python -c "from __future__ import print_function; import magic; print(dir(magic))" would also be useful in diagnosing this.

Looks like:

['MAGIC_CHECK', 'MAGIC_COMPRESS', 'MAGIC_CONTINUE', 'MAGIC_DEBUG', 'MAGIC_DEVICES', 'MAGIC_ERROR', 'MAGIC_MIME', 'MAGIC_MIME_ENCODING', 'MAGIC_NONE', 'MAGIC_NO_CHECK_APPTYPE', 'MAGIC_NO_CHECK_ASCII', 'MAGIC_NO_CHECK_COMPRESS', 'MAGIC_NO_CHECK_ELF', 'MAGIC_NO_CHECK_FORTRAN', 'MAGIC_NO_CHECK_SOFT', 'MAGIC_NO_CHECK_TAR', 'MAGIC_NO_CHECK_TOKENS', 'MAGIC_NO_CHECK_TROFF', 'MAGIC_PRESERVE_ATIME', 'MAGIC_RAW', 'MAGIC_SYMLINK', 'Magic', 'MagicException', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '_get_magic_type', '_instances', '_magic_buffer', '_magic_file', '_magic_load', 'c_char_p', 'c_int', 'c_size_t', 'c_void_p', 'coerce_filename', 'ctypes', 'dll', 'errorcheck_negative_one', 'errorcheck_null', 'from_buffer', 'from_file', 'glob', 'libmagic', 'magic_buffer', 'magic_check', 'magic_close', 'magic_compile', 'magic_errno', 'magic_error', 'magic_file', 'magic_load', 'magic_open', 'magic_setflags', 'magic_t', 'maybe_decode', 'os', 'sys', 'threading']

for me with python-magic==0.4.12.

[frabcus]

Turned out the problem was my global (installed via an Ubuntu package) version of nosetests getting found before the one in my virtualenv. Fine now and merging.