(cherry picked from commit c0366b78)

Conflicts:
	bt5/erp5_accounting/bt/revision

Conflicts:
	bt5/erp5_credential/bt/revision

* Method is activated with max_retry 0 and no retry on conflict error
* Document is not modified in case of multiple recipients

also simplify some error messages

This is mostly to avoid problems with proxy fields not finding their template field in default skin selection

Signed-off-by: Aurélien Calonne <aurel@nexedi.com>

getModificationDate: sometimes _p_serial cannot be used for DateTime ( TimeError: The time -2208988800.000000 is beyond the range of this Python implementation. )

When running multiple parralel ingestion updating documents inplace,
manage_delObjects complains that object is already removed (which is not the
case)

Note that after applying this change it's important to clear preferred timezone
for system preferences, as they have priority over user preferences

LongRequestLogger from zope svn which should support mutiple thread according to Leonardo + hack to log mysql query

ERP5VCS: fix error with recent versions of Git when there's no upstream configured for current branch

constraint_type should be a string instead of a list.

fixup! fix unicodeconflictresolver that was causing the same error when logging the problematic text