A release blocking change[1] is adding an exception for a timeout acquiring a connection object from a pool. This string change is meant to help ensure we have clearly communicated the error case. This change has not merged as of the writing of this email but is pending final review. Bringing it to the attention of this list per the wiki [2].  [1] https://review.openstack.org/#/c/119452  [2] https://wiki.openstack.org/wiki/StringFreeze