endme

Error:
2019-07-21 20:17:20,644: Exception on /register [POST]
Traceback (most recent call last):
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/flask/app.py", line 2311, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/flask/app.py", line 1835, in full_dispatch_request
    return self.finalize_request(rv)
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/flask/app.py", line 1852, in finalize_request
    response = self.process_response(response)
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/flask/app.py", line 2133, in process_response
    self.session_interface.save_session(self, ctx.session, response)
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/flask_session/sessions.py", line 355, in save_session
    total_seconds(app.permanent_session_lifetime))
  File "/home/8BitRebellion/.virtualenvs/my-virtualenv/lib/python3.6/site-packages/werkzeug/contrib/cache.py", line 839, in set
    pickle.dump(value, f, pickle.HIGHEST_PROTOCOL)
TypeError: can't pickle _thread.RLock objects
__________________________________________________________________
Code:
@app.route("/register", methods=["GET", "POST"])
def register():

    if request.method == "POST":
        if not request.form.get("email") or not request.form.get("username") or not request.form.get("password") or request.form.get("password") != request.form.get("confirmation"):
            return apology("retry", 400)
        exe = """INSERT INTO users (username, hash, email, created, perms)
            VALUES(""" + sanitize(request.form.get('username')) + ',' + sanitize(pwd_context.hash(request.form.get('password'))) + ',' + sanitize(request.form.get('email')) + ',' + sanitize(datetime.utcnow()) + ',' + sanitize(datetime.utcnow()) + ')'
        # insert the new user into users, storing the hash of the user's password
		# sanitize and apology are my own functions
		# LINE THAT CAUSES THE ERROR
        result = db.session.execute(exe)

        if not result:
            return apology("Username already exists.")

        # remember which user has logged in
        session["user_id"] = result

        # redirect user to home page
        return redirect(url_for("index"))

    elif request.method == "GET":
        return render_template("register.html")