BusinessTemplate: fix NameError on view when erp5_forge is not updated

This only happens in rare condition:
 * products where updated and ERP5VCS is moved to portal_components
 * everything is updated except erp5_forge
 * preferences for VCS working copies is set

product/ERP5/Document/BusinessTemplate.py

@@ -5816,8 +5816,11 @@ Business Template is a set of definitions, such as skins, portal types and categ
       # could be moved to Products.ERP5.Base.Base
       try:
         from erp5.component.module.WorkingCopy import NotAWorkingCopyError
+      except ImportError:
+        return False
+      try:
         return self.getVcsTool().reference in vcs
-      except (ImportError, NotAWorkingCopyError):
+      except NotAWorkingCopyError:
         return None in vcs
 
     security.declareProtected(Permissions.ManagePortal, 'export')

[Jérome Perrin]

I tried several approaches, but there's no regression test for this exact problem, because it happens only with "not fully" updated site.

While trying to reproduce, I could improve a bit test coverage in !992 (merged) , !996 (merged) and !989 (merged) I was first thinking that this problem only happens when erp5_forge is not installed and we don't notice because testXHTMLStyle just check all business templates together, so I tried to run this html style on business templates one by one, to reproduce that situation when we don't have erp5_forge installed, but it's not enough to reproduce that problem.

Pylint did not help here either. I tried other checkers, with this minimal reproduction:

"repro for https://lab.nexedi.com/nexedi/erp5/commit/7d3c55e2a5a21223d46ccd661a7c2a7f4116fad4"
try:
    from notexist import Error # type: ignore
except (ImportError, Error):
    pass

it fails at runtime

Traceback (most recent call last):
  File "repro.py", line 3, in <module>
    from notexist import Error
ImportError: No module named 'notexist'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "repro.py", line 4, in <module>
    except (ImportError, Error):
NameError: name 'Error' is not defined

Out of the tools I tried, only https://github.com/google/pytype recognize this error:

$ for tool in pylint pyflakes mypy pytype ; do echo $tool ; $tool repro.py ; echo  ; done
pylint

--------------------------------------------------------------------
Your code has been rated at 10.00/10 (previous run: 10.00/10, +0.00)


pyflakes

mypy
Success: no issues found in 1 source file

pytype
Computing dependencies
Analyzing 1 sources with 0 local dependencies
ninja: Entering directory `/tmp/xxx/.pytype'
[1/1] check repro
FAILED: /tmp/xxx/.pytype/pyi/repro.pyi 
pytype-single --imports_info /tmp/xxx/.pytype/imports/repro.imports --module-name repro -V 3.5 -o /tmp/xxx/.pytype/pyi/repro.pyi --analyze-annotated --nofail --quick /tmp/xxx/repro.py
File "/tmp/xxx/repro.py", line 4, in <module>: Name 'Error' is not defined [name-error]

For more details, see https://google.github.io/pytype/errors.html#name-error.
ninja: build stopped: subcommand failed.