diff --git a/chronographer/event_handlers.py b/chronographer/event_handlers.py
index 0f35cc7..04b8ef7 100644
--- a/chronographer/event_handlers.py
+++ b/chronographer/event_handlers.py
@@ -119,7 +119,7 @@ async def on_pr(event):
     pr_labels = {label['name'] for label in pull_request['labels']}
     diff_url = (
         f'https://github.com/{repo_slug}'
-        f'/pull/{pull_request["number"]:d}.diff'
+        f'/pull/{pull_request['number']:d}.diff'
     )
     head_branch = pull_request['head']['ref']
     head_sha = pull_request['head']['sha']
@@ -187,7 +187,7 @@ async def on_pr(event):
                         'title':
                             f'{checks_summary_title_prefix!s}'
                             'Nothing to do — change note not required',
-                        'text': f'Labels: {", ".join(pr_labels)}',
+                        'text': f'Labels: {', '.join(pr_labels)}',
                         'summary':
                             'Heeeeey!'
                             '\n\n'
@@ -266,7 +266,7 @@ async def on_pr(event):
         'Check run ID is %s',
         resp['id'],
     )
-    check_runs_updates_uri = f'{check_runs_base_uri}/{resp["id"]:d}'
+    check_runs_updates_uri = f'{check_runs_base_uri}/{resp['id']:d}'
 
     logger.info("Here's the diff URL: %s", diff_url)
     diff_text = await gh_api.getitem(
@@ -315,7 +315,7 @@ async def on_pr(event):
     )
 
     if news_fragments_added and fragment_provided_label is not None:
-        labels_url = f'{pull_request["issue_url"]}/labels'
+        labels_url = f'{pull_request['issue_url']}/labels'
         await gh_api.post(
             labels_url,
             preview_api_version='symmetra',
diff --git a/requirements.txt b/requirements.txt
index 15c553d..82eb025 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -650,9 +650,9 @@ urllib3==2.2.2 \
     --hash=sha256:a448b2f64d686155468037e1ace9f2d2199776e17f0a46610480d311f73e3472 \
     --hash=sha256:dd505485549a7a552833da5e6063639d0d177c04f23bc3864e41e5dc5f612168
     # via sentry-sdk
-virtualenv==20.26.3 \
-    --hash=sha256:4c43a2a236279d9ea36a0d76f98d84bd6ca94ac4e0f4a3b9d46d05e10fea542a \
-    --hash=sha256:8cc4a31139e796e9a7de2cd5cf2489de1217193116a8fd42328f1bd65f434589
+virtualenv==20.26.6 \
+    --hash=sha256:280aede09a2a5c317e409a00102e7077c6432c5a38f0ef938e643805a7ad2c48 \
+    --hash=sha256:7345cc5b25405607a624d8418154577459c3e0277f5466dd79c49d5e492995f2
     # via pre-commit
 yarl==1.9.4 \
     --hash=sha256:008d3e808d03ef28542372d01057fd09168419cdc8f848efe2804f894ae03e51 \