Expose close() method in client instances

- Enable pooled/keep-alive connections to be closed explicitly

botocore/client.py

@@ -601,6 +601,10 @@ def __getattr__(self, item):
                 self.__class__.__name__, item)
         )
 
+    def close(self):
+        """Closes underlying endpoint connections."""
+        self._endpoint.close()
+
     def _register_handlers(self):
         # Register the handler required to sign requests.
         service_id = self.meta.service_model.service_id.hyphenize()

botocore/endpoint.py

@@ -96,6 +96,9 @@ def __init__(self, host, endpoint_prefix, event_emitter,
     def __repr__(self):
         return '%s(%s)' % (self._endpoint_prefix, self.host)
 
+    def close(self):
+        self.http_session.close()
+
     def make_request(self, operation_model, request_dict):
         logger.debug("Making request for %s with params: %s",
                      operation_model, request_dict)

botocore/httpsession.py

@@ -242,6 +242,11 @@ def _get_request_target(self, url, proxy_url):
     def _chunked(self, headers):
         return headers.get('Transfer-Encoding', '') == 'chunked'
 
+    def close(self):
+        self._manager.clear()
+        for manager in self._proxy_managers.values():
+            manager.clear()
+
     def send(self, request):
         try:
             proxy_url = self._proxy_config.proxy_url_for(request.url)