Merge pull request #2208 from guerler/fix_error_message_001

[16.04] Add fixed validation check for data_source tools URL parameter

lib/galaxy/webapps/galaxy/controllers/tool_runner.py

@@ -69,6 +69,8 @@ def __tool_404__():
         # do param translation here, used by datasource tools
         if tool.input_translator:
             tool.input_translator.translate( params )
+        if 'runtool_btn' not in params.__dict__ and 'URL' not in params.__dict__:
+            error( 'Tool execution through the `tool_runner` requires a `runtool_btn` flag or `URL` parameter.' )
         # We may be visiting Galaxy for the first time ( e.g., sending data from UCSC ),
         # so make sure to create a new history if we've never had one before.
         history = tool.get_default_history_by_trans( trans, create=True )