Fix: No traceback when Python interpreter is running with -P

There was code in dnf and dnf-automatic to support running them from
the git tree. This was a developer-oriented hack that should not exist
in production code. It assumed that when running an installed dnf,
the `sys.path[0]` contains `/usr/bin`. If not, it overwrites
the contents of `sys.path[0]`.

This is a problem when running the Python interpreter with the `-P`
parameter (meaning: Don't automatically prepend a potentially unsafe
path to sys.path such as the current directory, the script's directory
or an empty string.)

The fix removes this developer-oriented hack. Developers should instead
set PYTHONPATH in the environment.

bin/dnf-automatic.in

@@ -27,10 +27,6 @@ if here == '/usr/bin':
     # we never import Python modules from /usr/bin
     # removing this lowers the risk of accidental imports of weird files
     del sys.path[0]
-else:
-    # git checkout
-    dnf_toplevel = os.path.dirname(here)
-    sys.path[0] = dnf_toplevel
 
 import dnf.automatic.main
 sys.exit(dnf.automatic.main.main(sys.argv[1:]))

bin/dnf.in

@@ -52,11 +52,6 @@ if here == '/usr/bin':
     # we never import Python modules from /usr/bin
     # removing this lowers the risk of accidental imports of weird files
     del sys.path[0]
-else:
-    # git checkout
-    import os
-    dnf_toplevel = os.path.dirname(here)
-    sys.path[0] = dnf_toplevel
 
 from dnf.cli import main
 main.user_main(sys.argv[1:], exit_code=True)