Run tests for python 3.7 in CI and fix failing tests

.travis.yml

@@ -1,8 +1,11 @@
+dist: xenial
+sudo: true
 language: python
 
 python:
     - 3.5.3
     - 3.6
+    - 3.7
 
 env:
     matrix:
@@ -30,6 +33,14 @@ matrix:
           env: PYTHONASYNCIODEBUG=
           addons:
               mysql: 5.7
+        - python: 3.7
+          env: PYTHONASYNCIODEBUG=1
+          addons:
+              mariadb: 10.1
+        - python: 3.7
+          env: PYTHONASYNCIODEBUG=1
+          addons:
+              mysql: 5.7
 
 
 before_script:

aiomysql/sa/result.py

@@ -447,7 +447,7 @@ async def scalar(self):
         else:
             return None
 
-    async def __aiter__(self):
+    def __aiter__(self):
         return self
 
     async def __anext__(self):

aiomysql/utils.py

@@ -1,3 +1,4 @@
+import asyncio
 from collections.abc import Coroutine
 
 
@@ -70,9 +71,20 @@ async def __aexit__(self, exc_type, exc, tb):
 
 
 class _SAConnectionContextManager(_ContextManager):
-    async def __aiter__(self):
-        result = await self._coro
-        return result
+    def __aiter__(self):
+        return self
+
+    @asyncio.coroutine
+    def __anext__(self):
+        if self._obj is None:
+            self._obj = yield from self._coro
+
+        try:
+            return (yield from self._obj.__anext__())
+        except StopAsyncIteration:
+            self._obj.close()
+            self._obj = None
+            raise
 
 
 class _TransactionContextManager(_ContextManager):