# Buggy code
def get_unique_scan_id():
    scan_id = ""
    while scan_id == "":
        rand = "".join(
            random.choice(string.ascii_lowercase + string.digits) for _ in range(16)
        )
        count, context = current_app.elastic.gethost_scan_id(rand)
        if count == 0:
            scan_id = rand
    return scan_id


# Traceback (TypeError)
Nov 05 17:22:50 natlas-server bash[10026]: [2019-11-05 17:22:50,681] ERROR in app: Exception on /api/getwork [GET]
Nov 05 17:22:50 natlas-server bash[10026]: Traceback (most recent call last):
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
Nov 05 17:22:50 natlas-server bash[10026]:     response = self.full_dispatch_request()
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
Nov 05 17:22:50 natlas-server bash[10026]:     rv = self.handle_user_exception(e)
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
Nov 05 17:22:50 natlas-server bash[10026]:     reraise(exc_type, exc_value, tb)
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/_compat.py", line 35, in reraise
Nov 05 17:22:50 natlas-server bash[10026]:     raise value
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
Nov 05 17:22:50 natlas-server bash[10026]:     rv = self.dispatch_request()
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/venv/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
Nov 05 17:22:50 natlas-server bash[10026]:     return self.view_functions[rule.endpoint](**req.view_args)
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/app/auth/wrappers.py", line 41, in decorated_function
Nov 05 17:22:50 natlas-server bash[10026]:     return f(*args, **kwargs)
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/app/api/routes.py", line 70, in getwork
Nov 05 17:22:50 natlas-server bash[10026]:     count, context = current_app.elastic.gethost_scan_id(rand)
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/app/elastic.py", line 238, in gethost_scan_id
Nov 05 17:22:50 natlas-server bash[10026]:     if not self.checkStatus():
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/app/elastic.py", line 60, in checkStatus
Nov 05 17:22:50 natlas-server bash[10026]:     if not self.attemptReconnect():
Nov 05 17:22:50 natlas-server bash[10026]:   File "/opt/natlas/natlas-server/app/elastic.py", line 43, in attemptReconnect
Nov 05 17:22:50 natlas-server bash[10026]:     delta = now - self.lastReconnectAttempt
Nov 05 17:22:50 natlas-server bash[10026]: TypeError: unsupported operand type(s) for -: 'datetime.datetime' and 'NoneType

# Fixed code
def get_unique_scan_id():
    scan_id = ""
    while scan_id == "":
        rand = "".join(
            random.choice(string.ascii_lowercase + string.digits) for _ in range(16)
        )
        count, context = current_app.elastic.get_host_by_scan_id(rand)
        if count == 0:
            scan_id = rand
    return scan_id