Two asyncio changes that fix tests

Author: tannewt

asyncio/funcs.py

@@ -98,6 +98,9 @@ async def gather(*aws, return_exceptions=False):
 
     Returns a list of return values of all *aws*
     """
+    if not aws:
+        return []
+
     def done(t, er):
         # Sub-task "t" has finished, with exception "er".
         nonlocal state

asyncio/stream.py

@@ -113,6 +113,13 @@ def write(self, buf):
         `Stream.drain` is called. It is recommended to call `Stream.drain`
         immediately after calling this function.
         """
+        if not self.out_buf:
+            # Try to write immediately to the underlying stream.
+            ret = self.s.write(buf)
+            if ret == len(buf):
+                return
+            if ret is not None:
+                buf = buf[ret:]
 
         self.out_buf += buf