fix #4039
Merge pull request #4041 from giantlock/develop

fix #4039
Updated dev_requirements.txt
Updated environment test to use mock library.
Fetching tags does not require an upstream remote.
Updated development docs.
Added headers in creating virtualenv section.
Updated testing section.

Use dev_requirements.txt in order to run tests.
Merge pull request #4044 from rca/fix_environment_test

Fix environment test
Merge pull request #4045 from rca/update_hacking

Update hacking
Revert "modules.pacman - pacman -Syu is the wrong way to install a package imho"

This reverts commit b041658dd10c58d39a82d14a079e6a46b88ceb3c.
Merge remote-tracking branch 'upstream/develop' into develop