diff --git a/dab_mechanic/wikidata_oauth.py b/dab_mechanic/wikidata_oauth.py
index 5af0976..bafb54e 100644
--- a/dab_mechanic/wikidata_oauth.py
+++ b/dab_mechanic/wikidata_oauth.py
@@ -1,11 +1,17 @@
+"""Wikidata OAuth."""
+
+import typing
 from urllib.parse import urlencode
 
 from flask import current_app, session
+from requests.models import Response
 from requests_oauthlib import OAuth1Session
 
 wiki_hostname = "en.wikipedia.org"
 api_url = f"https://{wiki_hostname}/w/api.php"
 
+CallParams = dict[str, str | int]
+
 
 def get_edit_proxy() -> dict[str, str]:
     """Retrieve proxy information from config."""
@@ -16,7 +22,7 @@ def get_edit_proxy() -> dict[str, str]:
         return {}
 
 
-def api_post_request(params: dict[str, str | int]):
+def api_post_request(params: CallParams) -> Response:
     """HTTP Post using Oauth."""
     app = current_app
     client_key = app.config["CLIENT_KEY"]
@@ -27,11 +33,12 @@ def api_post_request(params: dict[str, str | int]):
         resource_owner_key=session["owner_key"],
         resource_owner_secret=session["owner_secret"],
     )
-    proxies = get_edit_proxy()
-    return oauth.post(api_url, data=params, timeout=10, proxies=proxies)
+    r: Response = oauth.post(api_url, data=params, timeout=10, proxies=get_edit_proxy())
+    return r
 
 
-def raw_request(params):
+def raw_request(params: CallParams) -> Response:
+    """Raw request."""
     app = current_app
     url = api_url + "?" + urlencode(params)
     client_key = app.config["CLIENT_KEY"]
@@ -42,43 +49,49 @@ def raw_request(params):
         resource_owner_key=session["owner_key"],
         resource_owner_secret=session["owner_secret"],
     )
-    proxies = get_edit_proxy()
-    return oauth.get(url, timeout=10, proxies=proxies)
+    r: Response = oauth.get(url, timeout=10, proxies=get_edit_proxy())
+    return r
 
 
-def api_request(params):
-    return raw_request(params).json()
+def api_request(params: CallParams) -> dict[str, typing.Any]:
+    """Make API request and return object parsed from JSON."""
+    return typing.cast(dict[str, typing.Any], raw_request(params).json())
 
 
-def get_token():
-    params = {
+def get_token() -> str:
+    """Get csrftoken from MediaWiki API."""
+    params: CallParams = {
         "action": "query",
         "meta": "tokens",
         "format": "json",
         "formatversion": 2,
     }
     reply = api_request(params)
-    token = reply["query"]["tokens"]["csrftoken"]
+    token: str = reply["query"]["tokens"]["csrftoken"]
 
     return token
 
 
-def userinfo_call():
+def userinfo_call() -> dict[str, typing.Any]:
     """Request user information via OAuth."""
-    params = {"action": "query", "meta": "userinfo", "format": "json"}
+    params: CallParams = {"action": "query", "meta": "userinfo", "format": "json"}
     return api_request(params)
 
 
-def get_username():
+def get_username() -> str | None:
+    """Get username for current user."""
     if "owner_key" not in session:
-        return  # not authorized
+        return None  # not authorized
 
     if "username" in session:
+        assert isinstance(session["username"], str)
         return session["username"]
 
     reply = userinfo_call()
     if "query" not in reply:
-        return
-    session["username"] = reply["query"]["userinfo"]["name"]
+        return None
+    username = reply["query"]["userinfo"]["name"]
+    assert isinstance(username, str)
+    session["username"] = username
 
-    return session["username"]
+    return username
diff --git a/templates/show_error.html b/templates/show_error.html
index e75e75e..dd79c3c 100644
--- a/templates/show_error.html
+++ b/templates/show_error.html
@@ -7,24 +7,17 @@
 {% block content %}
 <div class="p-2">
 
-<h1>Software error: {{ tb.exception_type }}</h1>
+<h1>Software error: {{ exception_type }}</h1>
 <div>
-  <pre>{{ tb.exception }}</pre>
+  <pre>{{ exception }}</pre>
 </div>
 
-{% set body %}
-URL: {{ request.url }}
-
-{{ tb.plaintext | safe }}
-{% endset %}
-
-<p><a class="btn btn-primary btn-lg" role="button" href="https://github.com/EdwardBetts/dab-mechanic/issues/new?title={{ tb.exception + " " + request.url | urlencode }}&body={{ body | urlencode }}">Submit as an issue on GitHub</a> (requires an account with GitHub)</p>
-
 <h2 class="traceback">Traceback <em>(most recent call last)</em></h2>
-{{ tb.render_summary(include_title=False) | safe }}
+{{ summary | safe }}
+
+<p>Error in function "{{ last_frame.f_code.co_name }}": {{ last_frame_args | pprint }}</p>
+<pre>{{ last_frame.f_locals | pprint }}</pre>
 
-<p>Error in function "{{ last_frame.function_name }}": {{ last_frame_args | pprint }}</p>
-<pre>{{ last_frame.locals | pprint }}</pre>
 </div>
 
 {% endblock %}
diff --git a/web_view.py b/web_view.py
index 2730f23..5809c6e 100755
--- a/web_view.py
+++ b/web_view.py
@@ -3,6 +3,8 @@
 import inspect
 import json
 import re
+import sys
+import traceback
 from typing import Optional
 
 import flask
@@ -10,7 +12,7 @@ import lxml.html
 import requests
 import werkzeug.exceptions
 from requests_oauthlib import OAuth1Session
-from werkzeug.debug.tbtools import get_current_traceback
+from werkzeug.debug.tbtools import DebugTraceback
 from werkzeug.wrappers import Response
 
 from dab_mechanic import mediawiki_api, wikidata_oauth, wikipedia
@@ -26,20 +28,31 @@ awdl_url = "https://dplbot.toolforge.org/articles_with_dab_links.php"
 
 
 @app.before_request
-def global_user():
+def global_user() -> None:
     """Make username available everywhere."""
     flask.g.user = wikidata_oauth.get_username()
 
 
 @app.errorhandler(werkzeug.exceptions.InternalServerError)
-def exception_handler(e):
-    tb = get_current_traceback()
-    last_frame = next(frame for frame in reversed(tb.frames) if not frame.is_library)
-    last_frame_args = inspect.getargs(last_frame.code)
+def exception_handler(e: werkzeug.exceptions.InternalServerError) -> tuple[str, int]:
+    """Handle exception."""
+    exec_type, exc_value, current_traceback = sys.exc_info()
+    assert exc_value
+    tb = DebugTraceback(exc_value)
+
+    summary = tb.render_traceback_html(include_title=False)
+    exc_lines = "".join(tb._te.format_exception_only())
+
+    last_frame = list(traceback.walk_tb(current_traceback))[-1][0]
+    last_frame_args = inspect.getargs(last_frame.f_code)
+
     return (
         flask.render_template(
             "show_error.html",
-            tb=tb,
+            plaintext=tb.render_traceback_text(),
+            exception=exc_lines,
+            exception_type=tb._te.exc_type.__name__,
+            summary=summary,
             last_frame=last_frame,
             last_frame_args=last_frame_args,
         ),
@@ -47,14 +60,15 @@ def exception_handler(e):
     )
 
 
-def parse_articles_with_dab_links(root: lxml.html.Element) -> list[tuple[str, int]]:
+def parse_articles_with_dab_links(root: lxml.html.HtmlElement) -> list[tuple[str, int]]:
     """Parse Articles With Multiple Dablinks."""
     articles = []
     table = root.find(".//table")
+    assert table is not None
     for tr in table:
         title = tr[0][0].text
         count_text = tr[1][0].text
-        assert count_text.endswith(" links")
+        assert title and count_text and count_text.endswith(" links")
         count = int(count_text[:-6])
 
         articles.append((title, count))
@@ -63,7 +77,8 @@ def parse_articles_with_dab_links(root: lxml.html.Element) -> list[tuple[str, in
 
 
 @app.route("/")
-def index():
+def index() -> str:
+    """Index page."""
     r = requests.get(awdl_url, params={"limit": 100})
     root = lxml.html.fromstring(r.content)
     articles = parse_articles_with_dab_links(root)
@@ -125,17 +140,17 @@ def save(enwiki: str) -> Response | str:
 
 def redirect_if_needed(enwiki: str) -> Optional[Response]:
     """Check if there are spaces in the article name and redirect."""
+    endpoint = flask.request.endpoint
+    assert endpoint
     return (
-        flask.redirect(
-            flask.url_for(flask.request.endpoint, enwiki=enwiki.replace(" ", "_"))
-        )
+        flask.redirect(flask.url_for(endpoint, enwiki=enwiki.replace(" ", "_")))
         if " " in enwiki
         else None
     )
 
 
 @app.route("/enwiki/<path:enwiki>")
-def article_page(enwiki: str) -> Response:
+def article_page(enwiki: str) -> Response | str:
     """Article Page."""
     redirect = redirect_if_needed(enwiki)
     if redirect:
@@ -151,7 +166,8 @@ def article_page(enwiki: str) -> Response:
 
 
 @app.route("/oauth/start")
-def start_oauth():
+def start_oauth() -> Response:
+    """Start OAuth."""
     next_page = flask.request.args.get("next")
     if next_page:
         flask.session["after_login"] = next_page
@@ -174,7 +190,8 @@ def start_oauth():
 
 
 @app.route("/oauth/callback", methods=["GET"])
-def oauth_callback():
+def oauth_callback() -> Response:
+    """Autentication callback."""
     client_key = app.config["CLIENT_KEY"]
     client_secret = app.config["CLIENT_SECRET"]
 
@@ -201,11 +218,12 @@ def oauth_callback():
     flask.session["owner_secret"] = oauth_tokens.get("oauth_token_secret")
 
     next_page = flask.session.get("after_login")
-    return flask.redirect(next_page) if next_page else flask.url_for("index")
+    return flask.redirect(next_page if next_page else flask.url_for("index"))
 
 
 @app.route("/oauth/disconnect")
-def oauth_disconnect():
+def oauth_disconnect() -> Response:
+    """Disconnect OAuth."""
     for key in "owner_key", "owner_secret", "username", "after_login":
         if key in flask.session:
             del flask.session[key]