The unit tests are currently failing due to missing imports. This commit
addresses this issue.
Additionally, TestIsUnixDomainSocket expects an error to be raised by
IsUnixDomainSocket if the file does not exist, but on Windows we do not
raise such error.
This issue is addressed by Stat-ing the file, and checking
if the file exists or not. We're also handling the case in which the given
filePath is a named pipe, returning false immediately, instead of trying to
dial it as a Unix domain socket.
