bitbake: prserv/serv: Improve error message when prserver cannot bind to supplied host address

If localhost resolves to a remote address (due to a misconfigured network),
starting the pr server will fail without useful information.

To reproduce, add '<bogus ip> localhost' to /etc/hosts and run
'bitbake -p'. The error message will be:

ERROR: Timeout while attempting to communicate with bitbake server
ERROR: Could not connect to server False:

Running 'bitbake-prserv --host=localhost --port=0 --start' will fail with:

error: [Errno 99] Cannot assign requested address

Since these errors does not show the IP address of the attempted socket
binding, this results in a lot of wasted time looking at firewall rules, etc.

This patch results in the following error message if the socket binding fails:

PR Server unable to bind to <bogus ip>:0

(Bitbake rev: fae5914030bcf4c061c22fc61034c40c87b7121a)

Signed-off-by: Konrad Scherer <Konrad.Scherer@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/prserv/serv.py

@@ -38,8 +38,17 @@ singleton = None
 class PRServer(SimpleXMLRPCServer):
     def __init__(self, dbfile, logfile, interface, daemon=True):
         ''' constructor '''
-        SimpleXMLRPCServer.__init__(self, interface,
-                                    logRequests=False, allow_none=True)
+        import socket
+        try:
+            SimpleXMLRPCServer.__init__(self, interface,
+                                        logRequests=False, allow_none=True)
+        except socket.error:
+            ip=socket.gethostbyname(interface[0])
+            port=interface[1]
+            msg="PR Server unable to bind to %s:%s\n" % (ip, port)
+            sys.stderr.write(msg)
+            raise PRServiceConfigError
+
         self.dbfile=dbfile
         self.daemon=daemon
         self.logfile=logfile