Registration may return 491

[tayler6000]

If you're trying to make a call, simply do phone.call(number) after phone.start()

Worked great in my case to make calls, but I was having random issues when connecting to Grandstream UCM6202V1.5A 1.0.20.38 Then I noticed the Grandstream was returning code 491 (Request Pending) and this was incorrectly raising InvalidAccountInfoError. As a workaround I changed the line 1769 of SIP.py to if response.status == SIPStatus.OK or response.status == SIPStatus.REQUEST_PENDING:

Originally posted by @guijusto in https://github.com/tayler6000/pyVoIP/issues/71#issuecomment-1296046131