Include flake8-print plugin

This alerts us of stray print statements, which should never occur
because this is a non-TUI application.

.github/workflows/main.yaml

@@ -45,7 +45,7 @@ jobs:
       - name: Install
         run: |
           set -euo pipefail
-          pip install flake8
+          pip install flake8 flake8-print
       - name: Linting
         run: |
           python -m flake8 snikket_web

snikket_web/admin.py

@@ -542,8 +542,6 @@ async def edit_circle(id_: str) -> typing.Union[str, quart.Response]:
             )
 
         return redirect(url_for(".edit_circle", id_=id_))
-    else:
-        print(form.errors)
 
     return await render_template(
         "admin_edit_circle.html",

snikket_web/user.py

@@ -138,7 +138,6 @@ async def profile() -> typing.Union[str, quart.Response]:
             mimetype = file_info.mimetype
             data = file_info.stream.read()
             if len(data) > max_avatar_size:
-                print(len(data), max_avatar_size)
                 form.avatar.errors.append(EAVATARTOOBIG)
                 ok = False
             elif len(data) > 0: