Fix broken dependency URLs

[hunterchristian]

While running bash ./scripts/common.sh, I noticed the installation of pylint and astroid were failing with the following error message:

tar: Unrecognized archive format 

It turns out that the old bitbucket URLs were pointing to files that no longer exist. I replaced these URLs with their pythonhosted equivalents.

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[hunterchristian]

@googlebot I signed it!