title: Cannot run apache airflow after fresh install, python import error
body: <p>after a fresh install using <code>pip install apache-airflow</code>, any attempts to run airflow end with a python import error:</p>
  
  <pre><code>Traceback (most recent call last):
  File "/Users/\*/env/bin/airflow", line 26, in &lt;module&gt; from airflow.bin.cli import CLIFactory
  File "/Users/\*/env/lib/python3.7/site-packages/airflow/bin/cli.py", line 70, in &lt;module&gt; from airflow.www.app import (cached_app, create_app)
  File "/Users/\*/env/lib/python3.7/site-packages/airflow/www/app.py", line 26, in &lt;module&gt; from flask_wtf.csrf import CSRFProtect
  File "/Users/\*/env/lib/python3.7/site-packages/flask_wtf/__init__.py", line 17, in &lt;module&gt; from .recaptcha import \*
  File "/Users/\*/env/lib/python3.7/site-packages/flask_wtf/recaptcha/__init__.py", line 2, in &lt;module&gt; from .fields import \*
  File "/Users/\*/env/lib/python3.7/site-packages/flask_wtf/recaptcha/fields.py", line 3, in &lt;module&gt; from . import widgets
  File "/Users/\*/env/lib/python3.7/site-packages/flask_wtf/recaptcha/widgets.py", line 5, in &lt;module&gt; from werkzeug import url_encode
  ImportError: cannot import name 'url_encode' from 'werkzeug' (/Users/*/env/lib/python3.7/site-packages/werkzeug/__init__.py)
  </code></pre>