Bench Update TypeError: 'NoneType' object is not iterable (during Updating DocTypes for frappe)

Running bench update to fix a python email issue and received the following (running v11 and was up to date and site was working on Aug 7 2018)

Updating DocTypes for frappe        : [================================        ]Traceback (most recent call last):
  File "/usr/lib/python3.5/runpy.py", line 184, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.5/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 97, in <module>
    main()
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/bench_helper.py", line 18, in main
    click.Group(commands=commands)(prog_name='bench')
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/frappe/frappe-bench/env/lib/python3.5/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/__init__.py", line 25, in _func
    ret = f(frappe._dict(ctx.obj), *args, **kwargs)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/commands/site.py", line 222, in migrate
    migrate(context.verbose, rebuild_website=rebuild_website)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/migrate.py", line 41, in migrate
    frappe.model.sync.sync_all(verbose=verbose)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/sync.py", line 19, in sync_all
    sync_for(app, force, verbose=verbose, reset_permissions=reset_permissions)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/sync.py", line 56, in sync_for
    reset_permissions=reset_permissions, for_sync=True)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py", line 65, in import_file_by_path
    ignore_version=ignore_version, reset_permissions=reset_permissions)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/modules/import_file.py", line 123, in import_doc
    frappe.delete_doc(doc.doctype, doc.name, force=1, ignore_doctypes=ignore, for_reload=True)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/__init__.py", line 752, in delete_doc
    ignore_permissions, flags, ignore_on_trash, ignore_missing)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/model/delete_doc.py", line 98, in delete_doc
    delete_for_document(doc)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/utils/global_search.py", line 348, in delete_for_document
    name = %s''', (doc.doctype, doc.name), as_dict=True)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/database.py", line 237, in sql
    ret = self.fetch_as_dict(formatted, as_utf8)
  File "/home/frappe/frappe-bench/apps/frappe/frappe/database.py", line 303, in fetch_as_dict
    keys = [column[0] for column in self._cursor.description]
TypeError: 'NoneType' object is not iterable

I don’t know if this was timing or not but ran

bench clear-cache

and ran

bench update

error was gone this time around and site is back up and running