fix EAGAIN reference

Author: vladak

adafruit_minimqtt/adafruit_minimqtt.py

@@ -477,7 +477,7 @@ def _send_bytes(
             try:
                 bytes_sent += self._sock.send(view[bytes_sent:])
             except OSError as exc:
-                if exc.errno == EAGAIN:
+                if exc.errno == errno.EAGAIN:
                     continue
                 raise