Invalid URLs on auth flow returns a stacktrace

[jamietanna]

If using i.e. https://indiepaper.io/indieauth/?me=jvt.me, we get the following response back

HTTP/2 500 
content-type: application/json
content-length: 2522
date: Wed, 18 Mar 2020 20:43:28 GMT
x-amzn-requestid: 7714f99a-cbfd-40fd-95cc-7c66938d1e96
x-amz-apigw-id: JmotqG_yIAMFRDQ=
x-amzn-trace-id: Root=1-5e7287f0-f510fdc0bc98d77480797090;Sampled=0
x-cache: Error from cloudfront
via: 1.1 3059f113464f0880a3b72a834c64f65f.cloudfront.net (CloudFront)
x-amz-cf-pop: MAN50-C3
x-amz-cf-id: MFwQar4YnAr7X1ZUMSsHiL7M8L4oOiql8GlNoOB0nwKacvtakI73fQ==

"{'message': 'An uncaught exception happened while servicing this request. You can investigate this with the `zappa tail` command.', 'traceback': ['Traceback (most recent call last):\\n', '  File \"/var/task/handler.py\", line 505, in handler\\n    response = Response.from_app(self.wsgi_app, environ)\\n', '  File \"/var/task/werkzeug/wrappers.py\", line 939, in from_app\\n    return cls(*_run_wsgi_app(app, environ, buffered))\\n', '  File \"/var/task/werkzeug/test.py\", line 923, in run_wsgi_app\\n    app_rv = app(environ, start_response)\\n', '  File \"/var/task/zappa/middleware.py\", line 70, in __call__\\n    response = self.application(environ, encode_response)\\n', '  File \"/var/task/beaker/middleware.py\", line 156, in __call__\\n    return self.wrap_app(environ, session_start_response)\\n', '  File \"/var/task/pecan/middleware/recursive.py\", line 56, in __call__\\n    return self.application(environ, start_response)\\n', '  File \"/var/task/pecan/core.py\", line 840, in __call__\\n    return super(Pecan, self).__call__(environ, start_response)\\n', '  File \"/var/task/pecan/core.py\", line 683, in __call__\\n    self.invoke_controller(controller, args, kwargs, state)\\n', '  File \"/var/task/pecan/core.py\", line 574, in invoke_controller\\n    result = controller(*args, **kwargs)\\n', '  File \"/var/task/indiepaper/controllers/indieauth.py\", line 26, in index\\n    indieauth.request_authorization(me, session[\\'state\\'])\\n', '  File \"/var/task/indiepaper/indieauth.py\", line 34, in request_authorization\\n    endpoints = discover_endpoints(me)\\n', '  File \"/var/task/indiepaper/indieauth.py\", line 10, in discover_endpoints\\n    response = requests.get(me)\\n', '  File \"/var/task/requests/api.py\", line 72, in get\\n    return request(\\'get\\', url, params=params, **kwargs)\\n', '  File \"/var/task/requests/api.py\", line 58, in request\\n    return session.request(method=method, url=url, **kwargs)\\n', '  File \"/var/task/requests/sessions.py\", line 498, in request\\n    prep = self.prepare_request(req)\\n', '  File \"/var/task/requests/sessions.py\", line 441, in prepare_request\\n    hooks=merge_hooks(request.hooks, self.hooks),\\n', '  File \"/var/task/requests/models.py\", line 309, in prepare\\n    self.prepare_url(url, params)\\n', '  File \"/var/task/requests/models.py\", line 383, in prepare_url\\n    raise MissingSchema(error)\\n', \"requests.exceptions.MissingSchema: Invalid URL 'jvt.me': No schema supplied. Perhaps you meant http://jvt.me?\\n\"]}"

Ideally the response would be slightly friendlier, maybe returning Invalid URL 'jvt.me': No schema supplied. Perhaps you meant http://jvt.me??