Instead of printing the error message and
calling sys.exit() when a section not exists
or reading the file failed rais an Exception
from readconfig. Depending on the Value or IO-Error,
the caller can decide if he wants to exit or continue.
If an Exception reaches the wsgi utilities
it bubbles all the way up.
Change-Id: Ieb444f8c34e37f49bea21c3caf1c6c2d7bee5fb4
Closes-Bug: 1578321