Update from python2.7 to python3

.drone.yml

@@ -3,12 +3,12 @@ name: default
 
 steps:
 - name: build
-  image: python:2
+  image: python:3
   commands:
   - pip install platformio
   - pio run
 - name: upload
-  image: python:2
+  image: python:3
   commands:
   - make otaupload
 - name: release
@@ -20,4 +20,4 @@ steps:
       - .pioenvs/nodemcu/firmware.bin
       - .pioenvs/nodemcu/firmware.elf
   when:
-    event: tag
+    event: tag