Error/Warning for genattrib.py

[chinyeungli]

There is no error/warning for the genattrib. It uses the validation in the about.py and giving out errors and warnings that is related to the .ABOUT files but has nothing to do with the genattrib.

[chinyeungli]

The current implementation in genattrib.py uses the validation functions in about.py. However, perhaps, it validates too much??

Since the only things that need to be validated in this situation are the existance of the license files, the context of the files (not empty and have correct encoding) and the existence of the output path..

all others such as "File doesn't exist" may not be valid/useful.

For instance, the workflow process for some situation are:

1. Get the reported BOM
2. Generate the ABOUT files AND extract licenses from DJE to OUR LOCAL machine
3. Generate the attribution

The current code will return a lot of warnings/errors about file doesn't exist as, of couse, the "actual files/components" are in the VM or other location, not in OUR LOCAL machine

[chinyeungli]

prompt/output error/warning if there is any component fail to generate attribution.