also str representation of unicode character is different.

Call the original method instead of copy/pasting the code

We still keep the following patches:
 - user: this is an ERP5 addition and maybe we use it in customer project
   code (if we don't I'm in favor of removing the feature, it's used in
   only one place in this repo)
 - call `self.changeSkin(self.portal.getCurrentSkinName())`. Maybe this
   is needed for CMFCore tests and could be good to send upstream, I did
   not check this part

This reverts commit 8d81b128.

commit message was wrong

Call the original method instead of copy/pasting the code

The original method will use .encode() on the basic= argument, so it
needs to be an ascii str or an unicode on python2, we had to change
some callers to pass basic= as text, to prevent:

     File "eggs/Zope-4.5.3+slapospatched001-py2.7.egg/Testing/ZopeTestCase/functional.py", line 43, in wrapped_func
       return func(*args, **kw)
     File "eggs/Zope-4.5.3+slapospatched001-py2.7.egg/Testing/ZopeTestCase/functional.py", line 93, in publish
       env['HTTP_AUTHORIZATION'] = basic_auth_encode(basic)
     File "eggs/Zope-4.5.3+slapospatched001-py2.7.egg/ZPublisher/utils.py", line 91, in basic_auth_encode
       header = b'Basic ' + base64.b64encode(value.encode('latin-1'))
   UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 2: ordinal not in range(128)

ValidationFailed is now a "real" class from Products.ERP5Type.Core.Workflow