Fix broken jedi auto-completion with newest jedi

In jedi v0.11, parser has been refactored in and moved into a
separate `parso` package.

IPython/core/completer.py

@@ -1350,11 +1350,11 b' class IPCompleter(Completer):'
 
         try:
             # should we check the type of the node is Error ?
-            from jedi.parser.tree import ErrorLeaf
+            from parso.tree import ErrorLeaf
             next_to_last_tree = interpreter._get_module().tree_node.children[-2]
             completing_string = False
             if isinstance(next_to_last_tree, ErrorLeaf):
-                completing_string = interpreter._get_module().tree_node.children[-2].value[0] in {'"', "'"}
+                completing_string = next_to_last_tree.value[0] in {'"', "'"}
             # if we are in a string jedi is likely not the right candidate for
             # now. Skip it.
             try_jedi = not completing_string

setup.py

@@ -185,7 +185,7 b' extras_require = dict('
 
 install_requires = [
     'setuptools>=18.5',
-    'jedi>=0.10',
+    'jedi>=0.11',
     'decorator',
     'pickleshare',
     'simplegeneric>0.8',