only build prs and main

.drone.yml

@@ -4,7 +4,7 @@ type: docker
 name: default
 
 steps:
-- name: qa
+- name: qa_main
   image: python:3.8-alpine
   commands:
   - apk add --no-cache gcc g++ musl-dev python3-dev
@@ -12,9 +12,18 @@ steps:
   - pipenv install --dev
   - pipenv run flake8
   - pipenv run python -m unittest discover ki
-
-trigger:
+  when:
     branch:
     - main
+
+- name: qa_pr
+  image: python:3.8-alpine
+  commands:
+  - apk add --no-cache gcc g++ musl-dev python3-dev
+  - pip3 install pipenv
+  - pipenv install --dev
+  - pipenv run flake8
+  - pipenv run python -m unittest discover ki
+  when:
     event:
     - pull_request