Fixes #448: Crash in Openshift / Kubernetes (#451)
Fixes #448: Crash in Openshift / Kubernetes (#451)

* Fixes #448: Crash in Openshift / Kubernetes

When using exchangelib in Openshift / Kubernetes where containers are
run as random userids, the getpwuid() produces an error.
With this change a default value is provided
ecederstrand/exchangelib