>>> from matplotlib import rcParams
>>> import os.path
>>> afm_fname = os.path.join(rcParams['datapath'],
...                         'fonts', 'afm', 'ptmr8a.afm')
>>>
>>> from matplotlib.afm import AFM
>>> with open(afm_fname) as fh:
...     afm = AFM(fh)

TypeError                                 Traceback (most recent call last)
<ipython-input-2-571314e27e20> in <module>()
      6 from matplotlib.afm import AFM
      7 with open(afm_fname) as fh:
----> 8     afm = AFM(fh)

~/dev/matplotlib/lib/matplotlib/afm.py in __init__(self, fh)
    341         """
    342         (dhead, dcmetrics_ascii, dcmetrics_name, dkernpairs, dcomposite) = \
--> 343             parse_afm(fh)
    344         self._header = dhead
    345         self._kern = dkernpairs

~/dev/matplotlib/lib/matplotlib/afm.py in parse_afm(fh)
    327 
    328     """
--> 329     _sanity_check(fh)
    330     dhead = _parse_header(fh)
    331     dcmetrics_ascii, dcmetrics_name = _parse_char_metrics(fh)

~/dev/matplotlib/lib/matplotlib/afm.py in _sanity_check(fh)
     99     # EndFontMetrics keyword must be the last non-empty line in the
    100     # file. We just check the first line.
--> 101     if not line.startswith(b'StartFontMetrics'):
    102         raise RuntimeError('Not an AFM file')
    103 

TypeError: startswith first arg must be str or a tuple of str, not bytes