When processing exception from _load do not allow overwriting it

If `self.loaded.pop` raises KeyError then this KeyError will be logged, not the 
initial exception from `self._load`.

powerline/lib/config.py

@@ -195,11 +195,11 @@ class ConfigLoader(MultiRunnedThread):
 			try:
 				self.loaded[path] = deepcopy(self._load(path))
 			except Exception as e:
+				self.exception('Error while loading {0}: {1}', path, str(e))
 				try:
 					self.loaded.pop(path)
 				except KeyError:
 					pass
-				self.exception('Error while loading {0}: {1}', path, str(e))
 				try:
 					self.loaded.pop(path)
 				except KeyError: