wip: make those old tests pass

git-svn-id: https://svn.code.sf.net/p/apertium/svn/trunk/lttoolbox@49958 72bbbca6-d526-0410-a7d9-f06f51895060
tests actually pass now; simplified complex tests for invalid input

No need to test the exact output for invalid input, it'll just crash anyway

git-svn-id: https://svn.code.sf.net/p/apertium/svn/trunk/lttoolbox@49959 72bbbca6-d526-0410-a7d9-f06f51895060
tests: use python's own subprocess module, simplify tests even more

git-svn-id: https://svn.code.sf.net/p/apertium/svn/trunk/lttoolbox@49960 72bbbca6-d526-0410-a7d9-f06f51895060