Add a testing method to open a activity with a uri

This can be used in the test to check if the activity can manage
different file formats.

src/sugar3/test/unittest.py

@@ -63,9 +63,19 @@ class UITestCase(unittest.TestCase):
             process.terminate()
 
     @contextmanager
-    def run_activity(self):
+    def run_activity(self, options=None):
+        self._run_activity(options)
+
+    @contextmanager
+    def run_activity_with_uri(self, uri):
+        self._run_activity(['--uri', uri])
+
+    def _run_activity(self, options=None):
         if self.bundle_id is not None:
-            process = subprocess.Popen(["sugar-launch", self.bundle_id])
+            cmd = ["sugar-launch", self.bundle_id]
+            if options is not None:
+                cmd += options
+            process = subprocess.Popen(cmd)
         else:
             print "No bundle_id specified."
             return