diff --git a/api/tests.py b/api/tests.py
index 7ce503c2..e69de29b 100644
--- a/api/tests.py
+++ b/api/tests.py
@@ -1,3 +0,0 @@
-from django.test import TestCase
-
-# Create your tests here.
diff --git a/common/migrations/0001_initial.py b/common/migrations/0001_initial.py
index db6f2e41..c01072dd 100644
--- a/common/migrations/0001_initial.py
+++ b/common/migrations/0001_initial.py
@@ -1,6 +1,5 @@
 # Generated by Django 3.0a1 on 2019-11-07 19:42
 
-import common.models
 from django.conf import settings
 from django.db import migrations, models
 import django.db.models.deletion
diff --git a/common/models.py b/common/models.py
index 9be1e75e..8740a938 100644
--- a/common/models.py
+++ b/common/models.py
@@ -143,7 +143,7 @@ def fix(s):
             days = ['po', 'ut', 'st', 'ct', 'pa', 'so', 'ne']
             self.day = days.index(fix(self.day.lower()))
             return self.day * 60 * 60 * 24 + self.time.hour * 60 * 60 + self.time.minute * 60
-        except ValueError as e:
+        except ValueError:
             return 0
 
     def summary(self, login, show_output=False):
diff --git a/survey/views.py b/survey/views.py
index 00ec63d8..2a3b84a0 100644
--- a/survey/views.py
+++ b/survey/views.py
@@ -132,7 +132,7 @@ def show(request, survey_file):
             "form": form,
             "survey": conf,
         })
-    except FileNotFoundError as e:
+    except FileNotFoundError:
         raise Http404()
     except SurveyError as e:
         if not is_teacher(request.user):
diff --git a/web/apps.py b/web/apps.py
index bd452bbf..23cb3428 100644
--- a/web/apps.py
+++ b/web/apps.py
@@ -4,5 +4,5 @@ class WebConfig(AppConfig):
     name = 'web'
 
     def ready(self):
-        import web.signals
+        import web.signals  # noqa: F401
 
diff --git a/web/tests.py b/web/tests.py
index 7ce503c2..e69de29b 100644
--- a/web/tests.py
+++ b/web/tests.py
@@ -1,3 +0,0 @@
-from django.test import TestCase
-
-# Create your tests here.
diff --git a/web/views/student.py b/web/views/student.py
index 9d95ef07..8c95fdc7 100644
--- a/web/views/student.py
+++ b/web/views/student.py
@@ -131,7 +131,7 @@ def get(submit):
     results = []
     try:
         results = EvaluationResult(submit.pipeline_path())
-    except json.JSONDecodeError as e:
+    except json.JSONDecodeError:
         # TODO: show error
         pass
 
@@ -836,7 +836,7 @@ def task_asset(request, task_name, path):
             if mime:
                 resp['Content-Type'] = f"{mime};charset=utf-8"
             return resp
-    except FileNotFoundError as e:
+    except FileNotFoundError:
         # Download directory as a .zip archive.
         # .tar.gz is also allowed as an extension to keep backwards compatibility
         archive_extensions = ['.tar.gz', '.zip']