Add test to check if Nginx is serving requests

.travis/dispatch.sh

@@ -23,6 +23,6 @@ else
 
     # TODO: don't hard-code this
     if [ "${SALT_NODE_ID}" = "servo-master1" ]; then
-        ./test.py sls.buildbot.master
+        ./test.py sls.buildbot.master sls.nginx
     fi
 fi

tests/sls/nginx/serving.py

@@ -0,0 +1,23 @@
+import urllib.request
+import urllib.error
+
+from tests.util import Failure, Success
+
+
+def run():
+    try:
+        urllib.request.urlopen('http://localhost/')
+    except urllib.error.URLError as e:
+        # Can call e.read() if there was a response but the HTTP status code
+        # indicated error; the method is unavailable if a connection could not
+        # be made. Nginx is reverse proxying Homu and Buildbot, which will be
+        # dead on Travis because the test pillar credentials are not valid.
+
+        # Also, we're 'expecting' a string for e.reason (for the connection
+        # refused error case), but it may be another exception instance.
+        if not hasattr(e, 'read'):
+            return Failure("Nginx is not serving requests:", str(e.reason))
+
+    # No need to catch HTTPError or ContentTooShortError specially here
+
+    return Success("Nginx is serving requests")