add unicode error catching

[ITJamie]

So i found this when i hit some non unicode files.

examples of some errors caught with this

this is a rough fix but at least allows tests to complete. without this catch the script would crash

unable to process file (path removed) due to unicode decode error
'utf-8' codec can't decode byte 0xa7 in position 195: invalid start byte
unable to process file (path removed) due to unicode decode error
'utf-8' codec can't decode byte 0xa1 in position 33: invalid start byte

The script probably shouldnt just assume a file is going to be utf8 encoded