pydal is not aware of ThreadSafeVariables

[carloshanson]

When using _enable_record_versioning() or table inheritance, an AttributeError is thrown. In either case the traceback is the same from pydal/base.py, line 656. The following is for table inheritance:

monster = db.Table(db, 'monster', Field('color'), Field('size'))
db.define_table('thing', Field('name'), monster)

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/chanson/py/py4web/apps/thing/__init__.py", line 7, in <module>
    from . models import db
  File "/home/chanson/py/py4web/apps/thing/models.py", line 9, in <module>
    db.define_table('thing', Field('name'), monster)
  File "/home/chanson/.local/share/virtualenvs/py4web-recc_4-8/lib/python3.6/site-packages/pydal/base.py", line 656, in define_table
    table = self.lazy_define_table(tablename, *fields, **kwargs)
  File "/home/chanson/.local/share/virtualenvs/py4web-recc_4-8/lib/python3.6/site-packages/pydal/base.py", line 676, in lazy_define_table
    if field.requires is DEFAULT:
  File "/home/chanson/.local/share/virtualenvs/py4web-recc_4-8/lib/python3.6/site-packages/threadsafevariable/__init__.py", line 16, in __get__
    return getattr(self.storage, "%s.%s" % (id(instance), id(self)))
  File "src/gevent/local.py", line 408, in gevent._local.local.__getattribute__
AttributeError: 'gevent._local.local' object has no attribute '139976984026752.139976984930736'