add juju.get_controllers

Fixes juju#529

juju/juju.py

@@ -1,4 +1,11 @@
+from juju.client.jujudata import FileJujuData
+
+
 class Juju(object):
+
+    def __init__(self, jujudata=None):
+        self.jujudata = jujudata or FileJujuData()
+
     def add_cloud(self, name, definition, replace=False):
         """Add a user-defined cloud to Juju from among known cloud types.
 
@@ -58,9 +65,8 @@ def get_clouds(self):
     def get_controllers(self):
         """Return list of all available controllers.
 
-        (maybe move this to Cloud?)
         """
-        raise NotImplementedError()
+        return self.jujudata.controllers()
 
     def get_plans(self, charm_url):
         """Return list of plans available for the specified charm.

tests/integration/test_juju.py

@@ -0,0 +1,16 @@
+import pytest
+
+from juju.juju import Juju
+from .. import base
+
+
+@base.bootstrapped
+@pytest.mark.asyncio
+async def test_get_controllers(event_loop):
+    async with base.CleanController() as controller:
+        j = Juju()
+
+        controllers = j.get_controllers()
+        assert isinstance(controllers, dict)
+        assert len(controllers) >= 1
+        assert controller.controller_name in controllers