cosmetic: tests/stubtest.py python26exports -> python27exports

Trivial cosmetic change to variable name.
Merge pull request #7 from moto-timo/cosmetic-python26exports-to-python27exports

cosmetic: tests/stubtest.py python26exports -> python27exports
added assertRaisesClr to handle clr exceptions without python equiv.

enabled test cases which used to crash on assertRaises - changed
to assertRaisesClr
enabled remaining tests in pythonmapper_core_test