tool verification: move no output assertion

from planemo the verify_tool function is called from
[within an try-except block](https://github.com/galaxyproject/planemo/blob/1aa3eb05a97ad20c0be6f6560ab5cec090e76612/planemo/engine/galaxy.py#L109)
which silently catches any exception.

Thus any exception raised from within verify_tool will not be
detected, i.e. the assertion needs to be moved into
`_verify_outputs` (which also seems to make sense by name)
in order to make verify_tool record the problem properly.

lib/galaxy/tool_util/verify/interactor.py

@@ -1430,8 +1430,6 @@ def verify_tool(
             raise e
 
         if not expected_failure_occurred:
-            assert data_list or data_collection_list
-
             try:
                 job_stdio = _verify_outputs(
                     testdef, test_history, jobs, data_list, data_collection_list, galaxy_interactor, quiet=quiet
@@ -1487,6 +1485,7 @@ def _handle_def_errors(testdef):
 
 
 def _verify_outputs(testdef, history, jobs, data_list, data_collection_list, galaxy_interactor, quiet=False):
+    assert data_list or data_collection_list, "Tool produced no output data"
     assert len(jobs) == 1, "Test framework logic error, somehow tool test resulted in more than one job."
     job = jobs[0]