Fix gulp builds failing when running managetests under upstart

Fixes #8

managetests/branches.py

@@ -102,8 +102,13 @@ class Branch:
             "rm -rf %s/%s/*" % (self.manager.caches_dir, self.name),
         ]
 
+        # Provide to the command the current environment plus $HOME
+        # gulp fails otherwise
+        env = dict(os.environ)
+        env["HOME"] = self.manager.build_dir
+
         for command in commands:
-            subprocess.call(command, shell=True)
+            subprocess.call(command, shell=True, env=env)
 
         self.manager.details["branches"][self.name] = self.mr
         self.manager.save_details()