Issue #16133: The asynchat.async_chat.handle_read() method now ignores

BlockingIOError exceptions. Initial patch written by Xavier de Gaye.

Document also in asyncore documentation that recv() may raise BlockingIOError.

Lib/asynchat.py

@@ -115,6 +115,8 @@ class async_chat(asyncore.dispatcher):
 
         try:
             data = self.recv(self.ac_in_buffer_size)
+        except BlockingIOError:
+            return
         except OSError as why:
             self.handle_error()
             return