Using Python's file open in 'r' mode opens it for text reading, which
converts all new lines to \n. Could use 'rb' binary mode, but then
don't have access to the string Template replacement functions. Thus,
force the output to have '\\r\\n' ending.
Also fix regex to match hex digits.
The USB VID&PID are automatically extracted from usbd_desc_cdc_msc.c
and inserted into pybcdc_inf.template, ensuring that the same USB
IDs get used everywhere