Error messages are wrapped in `'`

[MrCreosote]

There's extraneous quotes around error messages from the catalog:

In [9]: try:  
   ...:     bc.call_method("Catalog.get_module_version", [{ 
   ...:         "module_name": "njs_sdk_test_1foo.run", 
   ...:         "version": "beta", 
   ...:     }]) 
   ...: except Exception as e: 
   ...:     err = e 
   ...:      
   ...:                                                                         

In [10]: err                                                                    
Out[10]: biokbase.workspace.baseclient.ServerError("'Module cannot be found based on module_name or git_url parameters.'")

This is causing kb_sdk tests to fail, as the error messages used to not have these unnecessary quotes