specify mode for gzipfile (for python 3.9 compatibility)

[terriko]

In #910, @chazuttu noted the following:

Python 3.9 is the last version providing backward compatibility layers. 
Opening GzipFile file for writing without specifying the mode argument is deprecated

We should fix this by specifying the mode argument. You can read about the arguments in the documentation here:
https://docs.python.org/3/library/gzip.html

Without even looking at the code, my guess is that we want a mode of "rb" (read-only binary) where gzip is used, as we don't generally write to gzip files in cve-bin-tool.

[jerinjtitus]

I looked into this and I think it's already being accounted for. The mode is already specified everywhere.
If I am wrong, then please correct me

[terriko]

Hm. it's possible that it's been fixed since it was reported. Do all the gzipfile tests run correctly on python 3.9, now?

[chazuttu]

The mode for gzipfile can be of 'r', 'rb', 'a', 'ab', 'w', 'wb', 'x' or 'xb' for binary mode, or 'rt', 'at', 'wt', or 'xt' for text mode. The default is 'rb'.So I think its resolved.
U may close this issue

[terriko]

Thanks for double-checking for me!