This fixes the following error:

... WARNING ERP5Type.dynamic Could not load Component module 'erp5.component.document.WebServiceRequest'
Traceback (most recent call last):
  File ".../parts/erp5/product/ERP5Type/dynamic/component_package.py", line 476, in find_load_module
    return import_module(fullname)
 [... cut ...]
  File "<portal_components/document.erp5.WebServiceRequest>", line 41, in <module>
    from erp5.component.tool.WebServiceTool import ConnectionError
ComponentImportError: erp5.component.document.WebServiceRequest: cannot load Component WebServiceRequest :
Traceback (most recent call last):
  File ".../parts/erp5/product/ERP5Type/dynamic/component_package.py", line 392, in __load_module
    exec(source_code_obj, module.__dict__)
  File "<portal_components/document.erp5.WebServiceRequest>", line 41, in <module>
    from erp5.component.tool.WebServiceTool import ConnectionError
ImportError: cannot import name ConnectionError