fix ci yapf command if no python files found

.drone.jsonnet

@@ -21,7 +21,7 @@ local PipelineLinting = {
       },
       commands: [
         'pip install -qq yapf',
-        'yapf -dr ./',
+        '[ ! -z "$(find .  -type f -name *.py)" ] && yapf -rd ./',
       ],
     },
     {

.drone.yml

@@ -16,7 +16,7 @@ steps:
   image: python:3.9
   commands:
   - pip install -qq yapf
-  - yapf -dr ./
+  - "[ ! -z \"$(find .  -type f -name *.py)\" ] && yapf -rd ./"
   environment:
     PY_COLORS: 1
 
@@ -147,6 +147,6 @@ depends_on:
 
 ---
 kind: signature
-hmac: 56102913dd36d647039d11172139643b479f44079c46576b467abf403b8328af
+hmac: 9582b634b7a828ed530a37d26b86971e9da71a34c04e1d111b9ff3a39bf8cb7b
 
 ...