Place in project/__init__.py to patch the socket class during test runs to notify when a test attempts to connect to an external service

patch_socket.py

import sys

class TestTriedToAccessNetwork(BaseException):
    pass

if 'test' in sys.argv:
    import socket

    class PatchedSocket(socket.socket):
        def __init__(self, *args, **kwargs):
            super(PatchedSocket, self).__init__(*args, **kwargs)
        def connect(self, address):
            addr, _ = address
            if addr and addr != '127.0.0.1':
                #print "FAIL: %s" % addr
                #traceback.print_stack()
                raise TestTriedToAccessNetwork("Tried connecting to external resource: %s" % addr)
            super(PatchedSocket, self).connect(address)

    socket.socket = PatchedSocket

-            if addr and addr != '127.0.0.1':
+           if addr and addr not in ('127.0.0.1', 'localhost'):