error: different checksums!

[iainrist]

Due to hardware constraints, attempting to generate an 8-bit CRC using a 16-bit CRC.
pycrc gives different answers for its separate algorithms.

> python --version
Python 2.7.10
>python pycrc.py --width=8 --poly=0x105 --reflect-in=False --xor-in=0xfe --reflect-out=False --xor-out=0x00
0x91
> python pycrc.py --width=16 --poly=0x10500 --reflect-in=False --xor-in=0xfe00 --reflect-out=False --xor-out=0x00
pycrc.py: error: different checksums!
       bit-by-bit:        0x100
       bit-by-bit-fast:   0x9100
       table_driven:      0x9100

[tpircher-zz]

This can happen if a poly is even. Not all even polynomials are well-defined.
I'm not sure if this is possible to fix in general, I'd need to go back to paper and pencil. I'll mark this for a "future" milestone.