Detect Wifi adapters on OSX. Fixes #549.

gns3server/utils/asyncio/__init__.py

@@ -56,7 +56,7 @@ def subprocess_check_output(*args, cwd=None, env=None):
     if output is None:
         return ""
     # If we received garbage we ignore invalid characters
-    # it should happend only when user try to use another binary
+    # it should happens only when user try to use another binary
     # and the code of VPCS, dynamips... Will detect it's not the correct binary
     return output.decode("utf-8", errors="ignore")