list pool: order subnets by priority

adjust the db model for `Pool` to return the list of subnets
sorted by priority, which prohbably is what a user expects in general

additionally, fix `assertDictSubset()` to make sure msg is a string,
as it would sometimes fail, see 1and1#198

dim-testsuite/tests/util.py

@@ -48,10 +48,11 @@ def assertDictSubset(self, actual, expected, msg=None):
  if not (missing or mismatched):
  return
 
+ msg = ''
  if missing:
- msg = 'Missing: %s' % ','.join(safe_repr(m) for m in missing)
+ msg += 'Missing: %s' % ','.join(safe_repr(m) for m in missing)
  if mismatched:
- if msg:
+ if len(msg) > 0:
  msg += '; '
  msg += 'Mismatched values: %s' % ','.join(mismatched)
  self.fail(msg)

dim/dim/models/ip.py

@@ -120,7 +120,7 @@ class Pool(db.Model, WithAttr):
  vlan = relationship(Vlan)
  owner = relationship('Group')
  layer3domain = relationship(Layer3Domain)
- ipblocks = relationship("Ipblock", backref="pool")
+ ipblocks = relationship("Ipblock", backref="pool", order_by='Ipblock.priority')
  subnets = synonym('ipblocks')
 
  @property