Stop assuming that /usr/bin/python exists

[panos]

This proposed change will change all occasions of /usr/bin/python to the more agnostic /usr/bin/env python, similarly to the change here.

Relevant Trac ticket (Fixes 33192)

This pull request is a follow up to #1712 and was made due to issues regarding the tree that was used to make the changes. More information about this can be found in the Trac ticket itself. Some of the changes were adapted accordingly, but they are identical for the most part.

[coveralls]

Pull Request Test Coverage Report for Build 8125

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 63.408%

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Totals
Change from base Build 8113:	0.0%
Covered Lines:	50018
Relevant Lines:	78883

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💛 - Coveralls