graphite: fix the graphiteApi service

nixos/modules/services/monitoring/graphite.nix

···
   );
 
   graphiteApiConfig = pkgs.writeText "graphite-api.yaml" ''
-    time_zone: ${config.time.timeZone}
     search_index: ${dataDir}/index
+    ${optionalString (!isNull config.time.timeZone) ''time_zone: ${config.time.timeZone}''}
     ${optionalString (cfg.api.finders != []) ''finders:''}
     ${concatMapStringsSep "\n" (f: "  - " + f.moduleName) cfg.api.finders}
     ${optionalString (cfg.api.functions != []) ''functions:''}
···
         environment = {
           PYTHONPATH = let
               aenv = pkgs.python.buildEnv.override {
-                extraLibs = [ cfg.api.package pkgs.cairo ] ++ cfg.api.finders;
+                extraLibs = [ cfg.api.package pkgs.cairo pkgs.pythonPackages.cffi ] ++ cfg.api.finders;
               };
             in "${aenv}/${pkgs.python.sitePackages}";
           GRAPHITE_API_CONFIG = graphiteApiConfig;

nixos/tests/graphite.nix

···
   nodes = {
     one =
       { config, pkgs, ... }: {
+        time.timeZone = "UTC";
         services.graphite = {
-          web = {
+          web.enable = true;
+          api = {
             enable = true;
-          };
-          carbon = {
-            enableCache = true;
+            port = 8082;
           };
+          carbon.enableCache = true;
+          seyren.enable = true;
+          pager.enable = true;
         };
       };
-    };
+  };
 
   testScript = ''
     startAll;
     $one->waitForUnit("default.target");
     $one->requireActiveUnit("graphiteWeb.service");
+    $one->requireActiveUnit("graphiteApi.service");
+    $one->requireActiveUnit("graphitePager.service");
     $one->requireActiveUnit("carbonCache.service");
+    $one->requireActiveUnit("seyren.service");
     $one->succeed("echo \"foo 1 `date +%s`\" | nc -q0 localhost 2003");
     $one->waitUntilSucceeds("curl 'http://localhost:8080/metrics/find/?query=foo&format=treejson' --silent | grep foo")
   '';