Fix SyntaxError handling

[icemac]

When entering code containing a SyntaxError an error page is shown. Previously a warning was rendered above the text area containing the code.

Before (Zope 2.13):

After (Zope 4):

Besides the error page shown the changes are not saved!
Maybe this is caused by the changes in RestrictedPython.

[hannosch]

This might also be caused by changing some bare try/except to a try/except Exception. I think SyntaxError is derived from BaseException and thus might not be caught anymore.

[jamadden]

SyntaxError appears to be an Exception:

Python 2.7.14 (default, Sep 27 2017, 12:15:00)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.37)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> SyntaxError.mro()
[<type 'exceptions.SyntaxError'>,
 <type 'exceptions.StandardError'>,
 <type 'exceptions.Exception'>,
 <type 'exceptions.BaseException'>,
 <type 'object'>]

Python 3.4.7 (default, Sep 27 2017, 15:47:41)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.37)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> SyntaxError.mro()
[<class 'SyntaxError'>,
 <class 'Exception'>,
 <class 'BaseException'>,
 <class 'object'>]
>>>

[tseaver]

I'd prefer not to close bugs via PR merges in another repository: the bug here won't really be fixed until a new release of RestrictedPython is available.

[icemac]

@tseaver You are right, additionally Products.PythonScripts should depend on the new release to be able to leverage the bug fix here.

[tseaver]

@icemac Thanks for fixing the pin!