dependency hell problem for toolchain dockerization

Since moving to fossology-python 1.5.0 (!58 (merged)), toolchain dockerization does not work any more, because fossology-python 1.5.0 requires at least python 3.7, while scancode runs on python 3.6.

A solution must be found:

1. either we upgrade scancode version

• check json output differences
• check if also spdx-tools would need to be upgraded, and possible side effects of the upgrade

2. or we change scancode installation method for the dockerization

Solution 1 is a preferrable long term solution, but it may take too much time.