For python2.7 compatibility

Author: irachex

hyper/http20/connection.py

@@ -9,7 +9,7 @@
 from ..common.exceptions import ConnectionResetError
 from ..common.bufsocket import BufferedSocket
 from ..common.headers import HTTPHeaderMap
-from ..common.util import to_host_port_tuple, to_native_string
+from ..common.util import to_host_port_tuple, to_native_string, to_bytestring
 from ..packages.hyperframe.frame import (
     FRAMES, DataFrame, HeadersFrame, PushPromiseFrame, RstStreamFrame,
     SettingsFrame, Frame, WindowUpdateFrame, GoAwayFrame, PingFrame,
@@ -179,8 +179,8 @@ def request(self, method, url, body=None, headers={}):
             self.putheader(name, value, stream_id, replace=is_default)
 
         # Convert the body to bytes if needed.
-        if isinstance(body, str):
-            body = body.encode('utf-8')
+        if body:
+            body = to_bytestring(body)
 
         self.endheaders(message_body=body, final=True, stream_id=stream_id)