Improve workflow for missing arcanist certificates.

src/applications/conduit/controller/api/PhabricatorConduitAPIController.php

@@ -163,11 +163,8 @@ class PhabricatorConduitAPIController
     $session_key = idx($metadata, 'sessionKey');
     if (!$session_key) {
       return array(
-        'ERR-NO-CERTIFICATE',
-        'This server requires authentication but your client is not '.
-        'configured with an authentication certificate. Please refer to '.
-        '<http://www.phabricator.com/docs/phabricator/article/'.
-        'Installing_Arcanist_Certificates.html> for more info.',
+        'ERR-INVALID-SESSION',
+        'Session key is not present.'
       );
     }
 

src/applications/conduit/method/conduit/connect/ConduitAPI_conduit_connect_Method.php

@@ -62,10 +62,15 @@ class ConduitAPI_conduit_connect_Method extends ConduitAPIMethod {
         "allowed time range. Either your system clock is out of whack or ".
         "you're executing a replay attack.",
       "ERR-NO-CERTIFICATE" =>
-        "This server requires authentication but your client is not ".
-        "configured with an authentication certificate. Please refer to page ".
-        "http://www.phabricator.com/docs/phabricator/article/".
-        "Installing_Arcanist_Certificates.html for more info."
+        'This server requires authentication but your client is not '.
+        'configured with an authentication certificate. For instructions on '.
+        "installing Arcanist certificates, see the documentation:\n\n".
+        '    http://www.phabricator.com/docs/phabricator/article/'.
+        'Installing_Arcanist_Certificates.html'.
+        "\n\n".
+        "Retrieve your certificate for this server by logging into the web ".
+        "interface and going here:\n\n".
+        '    '.PhabricatorEnv::getProductionURI('/settings/page/arcanist/'),
     );
   }
 

src/docs/arcanist_certificates.diviner

@@ -19,7 +19,10 @@ like this:
 
 To retrieve the certificate for a Phabricator host:
 
-  - Login to Phabricator.
+  - Login to Phabricator. **Make sure you log into the installation you are
+    trying to install a certificate for!** If you are installing a certificate
+    for ##phabricator.example.com##, you need to log into
+    ##phabricator.example.com##, **not** ##secure.phabricator.com##.
   - Go to Settings (upper right, near Search) > Arcanist Certificate.
 
 Copy the host info including the certificate into the "hosts" section.