When submitting a request to "Read" ("Confirmation error"), the message "Approval error" appears in the message "Mechanism"

I am writing a web-crawl program with python and cannot log in using mechanize. The form on the site looks like this:

   <form method="post" action="PATLogon">
   <h2 align="center"><img src="/myaladin/images/aladin_logo_rd.gif"></h2>
   <!-- ALADIN Request parameters -->
  <input type=hidden name=req value="db">
  <input type=hidden name=key value="PROXYAUTH">
  <input type=hidden name=url value="http://eebo.chadwyck.com/search">
  <input type=hidden name=lib value="8">    
<table>
<tr><td><b>Last Name:</b></td>
    <td><input name=LN size=20 maxlength=26></td>
<tr><td><b>University ID or Library Barcode:</b></td>
    <td><input type=password name=BC size=20 maxlength=21></td>
<tr><td><b>Institution:</b></td>
    <td><select name="INST">
        <option value="??">Select University ----</option>
        <option value="AU">American</option>
        <option value="CU">Catholic</option>
        <option value="DC">District of Columbia</option>
        <option value="GA">Gallaudet</option>
        <option value="GM">George Mason</option>
        <option value="GW">George Washington</option>
        <option value="GT">Georgetown</option>
        <option value="MU">Marymount</option>
        <option value="TR">Trinity</option>
        </select>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
        <input type="submit" value="GO">
    </td></tr></table></form>

So, I can install everything correctly, but when I submitted the form and tried to print the answer, I was left with an error. My code is as follows:

 import mechanize
 import time
 br = mechanize.Browser()
 br.set_handle_robots(False)

 def connect():
     # connection information                                                    
     url = "https://www.aladin.wrlc.org/Z-WEB/Aladin?req=db&key=PROXYAUTH&lib=8&\url=http://eebo.chadwyck.com/search"
     br.open(url)
     time.sleep(0.5)
     br.select_form(nr=0)
     br["LN"] = "Reese"
     br["BC"] = "myPassword"
     br["INST"] = ["AU"]
     response = br.submit()
     print response.getheaders()

The error I get here is:

 >>> eebolib.connect()
 Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "eebolib.py", line 28, in connect
     print response.read()
   File "build/bdist.macosx-10.5-fat3/egg/mechanize/_response.py", line 190, in read
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 349, in read
     data = self._sock.recv(rbufsize)
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 553, in read
     if self.length is not None:
   File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 1282, in read
     if amt is None or amt > self._line_left:
 AssertionError

If someone can provide some help with this, I will be very grateful.