Fix handling of "no-cpp" test tag for error tests, where "cpp" is already removed from the list of test backends.
Fix handling of "no-cpp" test tag for error tests, where "cpp" is already removed from the list of test backends.

da-woods/cython,da-woods/cython,da-woods/cython,cython/cython,scoder/cython,scoder/cython,cython/cython,cython/cython,scoder/cython,cython/cython,scoder/cython,da-woods/cython