diff --git a/ippisite/ippidb/tasks.py b/ippisite/ippidb/tasks.py
index 0e090768cc7c960e5782a5be93e93d383548c9c2..2fe4374d4a2b4ddbbd3f24c58f25bfefda2a24e8 100644
--- a/ippisite/ippidb/tasks.py
+++ b/ippisite/ippidb/tasks.py
@@ -535,9 +535,9 @@ def run_le_lle_plot(self: MonitorTask):
     :type self: MonitorTask
     """
     self.update_state(state=states.STARTED)
-    self.write(std_out=f"Starting computing LE-LLE plot")
+    self.write(std_out="Starting computing LE-LLE plot")
     generate_le_lle_plot()
-    self.write(std_out=f"Finished computing LE-LLE plot")
+    self.write(std_out="Finished computing LE-LLE plot")
 
 
 @task(base=MonitorTask, bind=True)
@@ -549,9 +549,9 @@ def run_pca_plot(self: MonitorTask):
     :type self: MonitorTask
     """
     self.update_state(state=states.STARTED)
-    self.write(std_out=f"Starting computing PCA plot")
+    self.write(std_out="Starting computing PCA plot")
     generate_pca_plot()
-    self.write(std_out=f"Finished computing PCA plot")
+    self.write(std_out="Finished computing PCA plot")
 
 
 def launch_validate_contributions(contribution_ids: List[int]):
diff --git a/ippisite/ippidb/templatetags/customtags.py b/ippisite/ippidb/templatetags/customtags.py
index 1ea2c322293c7565d9c33e7c6525a84ebd83f900..1b65ab018fc7efb44f7524420a5a083cfa2f56d4 100644
--- a/ippisite/ippidb/templatetags/customtags.py
+++ b/ippisite/ippidb/templatetags/customtags.py
@@ -141,8 +141,8 @@ def bootstrap_core(object):
         # print form's error which are not related to a field but the form itself
         form = object
         for field in form:
-            for l in bootstrap_core(field):
-                ret.append(l)
+            for el in bootstrap_core(field):
+                ret.append(el)
     elif isinstance(object, ErrorList):
         # print errors in a bootstrap way
         for error in object:
diff --git a/ippisite/ippidb/tests/tests_contribute_e2e.py b/ippisite/ippidb/tests/tests_contribute_e2e.py
index d5d2877f34c23c64ad042d8bb78b75c0bd9be894..fce7c8ca4a9631d5f981ced39250c4848592d02e 100644
--- a/ippisite/ippidb/tests/tests_contribute_e2e.py
+++ b/ippisite/ippidb/tests/tests_contribute_e2e.py
@@ -230,7 +230,7 @@ class ContributionE2ETestCase(TestCase):
         self.assertEqual(
             response.url,
             reverse("contribution-detail", kwargs={"contribution_pk": 1}),
-            f"wrong final URL, should be the contribution permanent URL",
+            "wrong final URL, should be the contribution permanent URL",
         )
 
     def _generate_wizard_data(self, entry_data):
diff --git a/ippisite/ippisite/settings.template.py b/ippisite/ippisite/settings.template.py
index f6f6f702cfe02c599825ff16c4228906529f8181..cc7380331ae0fc0da893646062c37230ac094f0f 100644
--- a/ippisite/ippisite/settings.template.py
+++ b/ippisite/ippisite/settings.template.py
@@ -10,14 +10,15 @@ For the full list of settings and their values, see
 https://docs.djangoproject.com/en/1.10/ref/settings/
 """
 
+from django.utils.translation import gettext_lazy
 import os
 
 # set matplotlib backend
 import matplotlib
+
 matplotlib.use("agg")  # noqa: E402 BLK100
 
 # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
-from django.utils.translation import gettext_lazy
 
 BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))