Error on setparam in 0.4.1[78]

@mbarakaja reports:

I am not sure if this is related but my build started failing with this new version

h_inventory/fetch.py:131: in _validate
mimetype = magic.from_buffer(response.content, mime=True)
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:165: in from_buffer
m = _get_magic_type(mime)
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:139: in _get_magic_type
i = _instances[mime] = Magic(mime=mime)
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:76: in init
self.setparam(MAGIC_PARAM_NAME_MAX, 64)
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:113: in setparam
return magic_setparam(self.cookie, param, val)
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:322: in magic_setparam
return _magic_setparam(cookie, param, byref(v))
../../../virtualenv/python2.7.14/lib/python2.7/site-packages/magic.py:217: in errorcheck_negative_one
raise MagicException(err)
E MagicException: None

Start with the traceback in h_inventory/fetch.py:131, then inspect magic.py around _get_magic_type, Magic.init, setparam, and magic_setparam. Reproduce the failing call shown in the report and determine why MAGIC_PARAM_NAME_MAX raises MagicException: None; done means the reported setparam path completes without that exception.