fix the failing testEscaping unit test
fix the failing testEscaping unit test

previously, the get_store function did not raise an exception for
a store that doesn't exist

also change the following assertion to check the error message

scottp-dpaw/gsconfig,afabiani/gsconfig,boundlessgeo/gsconfig,garnertb/gsconfig.py,Geode/gsconfig,cristianzamar/gsconfig