title: How to flashing a message with link using Flask flash?
body: <p>I'm creating a web app using Flask to deal with GoogleOpenID, these codes are almost finished, except the flashing message contains a link:</p>
  
  <pre><code>@oid.after_login
  def create_or_login(resp):
      user = db_session.query(User).filter_by(email=resp.email).first()
      if user is not None:
          flash('Successfully signed in', 'success')
      else:
          user = User(nickname=resp.fullname, source=GOOGLE, email=resp.email)
          db_session.add(user)
          db_session.commit()
          flash(flashing_message, 'success')
      g.user = user
      session['nickname'] = user.nickname
      return redirect(oid.get_next_url())
  </code></pre>
  
  <p>It works well when flashing_message is like this: <code>'Successfully registered, please click here'</code></p>
  
  <p>But when flashing_message is <code>'Successfully registered, please click &lt;a href="/me" class="alert-link"&gt;here&lt;/a&gt;'</code>, it doesn't work (flashes nothing) without throwing any Error. Strangely, sentences between flash() and return doesn't work either (did not set session['nickname] or g.user).</p>