Merge tag 'sparks-2.7.2' into develop

2.7.2
Rework the PG admin account handling, display more informative messages and shell commands to achieve the result in a local environment where the user is supposed to have root/postgres permissions.
move the version into __init__.py, so we can do `import sparks; print sparks.version`.
Fix for non-relative import error message.
Nasty typo bug.
Remove shells from graphdev.
Hunting the "no .failed attribute" error.
Formattting bug. `.failed` seems OK now that we don't use .strip() prior testing it.
Add a comment about .strip() and .failed.
Fix formatting bad argument number.
Circumvent `pqsl` asking for "Password:" on standard output.
Do not install supervisor on a local environment, and don't try to restart_services() too.
bump version in setup.py
Merge branch 'release/2.7.3'