Fix py35 build

Author: jhgg

.travis.yml

@@ -18,4 +18,7 @@ after_success:
 matrix:
   include:
     - python: "3.5"
-      script: import-order graphql
+      script:
+        - flake8
+        - import-order graphql
+        - py.test --cov=graphql tests tests_py35

graphql/core/error.py

@@ -1,5 +1,5 @@
-from .language.location import get_location
 from .defer import DeferredException
+from .language.location import get_location
 
 
 class Error(Exception):

graphql/core/execution/middlewares/AsyncioExecutionMiddleware.py

@@ -1,10 +1,10 @@
 # flake8: noqa
-from asyncio import Future, coroutine, iscoroutine, ensure_future
+from asyncio import Future, ensure_future, iscoroutine
 from graphql.core.defer import Deferred
 
 
 def process_future_result(deferred):
-    def handle_future_result(future: Future):
+    def handle_future_result(future):
         exception = future.exception()
         if exception:
             deferred.errback(exception)

graphql/core/execution/parallel_execution.py

@@ -2,7 +2,7 @@
 import functools
 
 from graphql.core import ExecutionResult, Source, parse, validate
-from graphql.core.defer import Deferred, DeferredList, DeferredDict, defer, fail, succeed
+from graphql.core.defer import Deferred, DeferredDict, DeferredList, defer, fail, succeed
 from graphql.core.error import GraphQLError, format_error
 from graphql.core.execution import ExecutionContext, ResolveInfo, Undefined, collect_fields, default_resolve_fn, \
     get_argument_values, get_field_def, get_operation_root_type