Allow keepalive_timeout to be None

There was a bug in the library in that we could not both:

  * set keepalive_timeout as None
  * set force_close to True

Validation was wrong in that it expects `keepalive_timeout` to have to be
one of `float` or `int`, but it should also allow `None` since `aiohttp`
requires `keepalive_timeout` to be `None` if `force_close` is set to
`True`.

Closes aio-libs#932

aiobotocore/config.py

@@ -38,9 +38,9 @@ def _validate_connector_args(connector_args):
                     raise ParamValidationError(
                         report='{} value must be a boolean'.format(k))
             elif k in ['keepalive_timeout']:
-                if not isinstance(v, (float, int)):
+                if v is not None and not isinstance(v, (float, int)):
                     raise ParamValidationError(
-                        report='{} value must be a float/int'.format(k))
+                        report='{} value must be a float/int or None'.format(k))
             elif k == 'force_close':
                 if not isinstance(v, bool):
                     raise ParamValidationError(

tests/test_config.py

@@ -28,6 +28,11 @@ def test_connector_args():
         connector_args = dict(force_close="1")
         AioConfig(connector_args)
 
+    with pytest.raises(ParamValidationError):
+        # wrong type
+        connector_args = dict(keepalive_timeout="1")
+        AioConfig(connector_args)
+
     with pytest.raises(ParamValidationError):
         # wrong type
         connector_args = dict(ssl_context="1")
@@ -43,10 +48,11 @@ def test_connector_args():
         connector_args = dict(foo="1")
         AioConfig(connector_args)
 
-    # Test valid config:
+    # Test valid configs:
     AioConfig({
         "resolver": aiohttp.resolver.DefaultResolver()
     })
+    AioConfig({'keepalive_timeout': None})
 
     # test merge
     cfg = Config(read_timeout=75)