When no match for the platform is found in the software configuration
dictionary in impl/mozfetcher/_config.py then the "default" entry is
used if exists. In order to run an independently upgraded system-wide
xulrunner version the use of unsigned versions is made possible.
The attempt is made to modify some of the linked files in the root
directory of a runnung application (i.e. build/name). However, the
original file a link is pointed to may not be write-accessible for
the running process (in the case the application path is passed from
one user to another, or it is a system-wide installation of an example
application). When that is the case, the symlink is substituted with
the write-accessible copy.
Symlink (fallback to copy) the 'test_harness' module to the home
modules directory ("~/.chromeless/modules/internal) and write the
test output script to that module copy. Thus, the contents of
the original module directory are not modified.