Update unit tests for Python 3.5 compatability

Python 3.5 makes some changes in the exact TypeError messages used when it comes to the Python Buffer Protocol.

Specifically for Dbase32, the C backend TypeError messages will differ on Python 3.4 vs 3.5 when the "y#" and "s#" formats are used with PyArg_ParseTuple(), which effects 4 of the 6 dbase32 functions:

dbase32.db32enc()
dbase32.db32dec()
dbase32.isdb32()
dbase32.check_db32()

For example, Python 3.4:

>>> from dbase32 import db32dec
>>> db32dec(76)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' does not support the buffer interface

Vs Python 3.5:

>>> from dbase32 import db32dec
>>> db32dec(76)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: a bytes-like object is required, not 'int'

So the Dbase32 unit tests need to be updated to test against the new TypeError message format for Python >= 3.5, while still also being able to test against the old TypeError format for Python < 3.5, as Python 3.4 support isn't being dropped. (Actually, Dbase32 should still be compatible with Python 3.3 as well, but that's not actively tested by me anymore, so YMMV.)

A small update is also needed in the pure-Python dbase32._dbase32py fallback/reference implementation as it emulates the TypeError behaviour of the "y#" and "s#" C formats.