acmebot, uwsgi-python, debian-repo: fix linter issues

acmebot/tasks/main.yml

@@ -94,4 +94,3 @@
     src: /opt/acmebot/logrotate.d/acmebot
     dest: /etc/logrotate.d/acmebot
     state: link
-    

debian-repository/tasks/main.yml

@@ -22,4 +22,3 @@
     shell: /usr/bin/nologin
     createhome: false
     state: present
-

uwsgi-python/tasks/apps/alumnigraph.yml

@@ -9,9 +9,11 @@
     group: "{{app_group}}"
 
 - name: ensure data model upgrades are applied  # noqa 301
-  shell: "FLASK_APP={{app_program}} {{app_venv}}/bin/flask db upgrade"
+  command: "{{app_venv}}/bin/flask db upgrade"
   args:
     chdir: "{{app_path}}"
+  environment:
+    FLASK_APP: "{{app_program}}"
   become: true
   become_user: "{{app_user}}"
   notify: