title: attribute error: list object has not attribute lstrip in sending an email with attachment
body: <p>i am attaching a file from a particular path   c:\important\log.txt</p>
  
  <pre><code>sender = 'poojagupta4112@gmail.com'
  receiver = ['shubh4112@gmail.com']
  message = """From: From Pooja Gupta &lt;poojagupta4112@gmail.com&gt;
  To: To Shubha Goel &lt;shubh4112@gmail.com&gt;
  Subject: SMTP e-mail test
  
  This is a test e-mail message.
  """
  
  file_name = 'C:\important\log.txt'
  msg=MIMEMultipart()
  msg['From'] = sender
  msg['To'] = receiver
  msg['Subject'] = message
  msg['Date'] = email.Utils.formatdate(localtime=True)
  
  # build the attachment
  att = MIMEBase('application', 'base64')
  att.set_payload(open(file_name, 'rb').read())
  email.Encoders.encode_base64(att)
  att.add_header('Content-Disposition', 'attachment; filename="%s"' % os.path.basename(file_name))
  msg.attach(att)
  
  print 'successfully built attachment'
  try:
      session = smtplib.SMTP('smtp.gmail.com',587)
      print 'Starting..'
      session.ehlo()
      print 'ehlo executed..'
      session.starttls()
      print 'starttls done'
  
      session.login(sender,'snxzoumwhpybzvmo')
      print 'logged in'
      session.sendmail(sender,receiver,msg.as_string())
      print 'sendmail executed..now quitting'
      session.close()
  
  except smtplib.SMTPRecipientsRefused:
      print 'Recipient refused'
  except smtplib.SMTPAuthenticationError:
      print 'Auth error'
  except smtplib.SMTPSenderRefused:
      print 'Sender refused'
  except smtplib.SMTPException:
      print('Error')
  </code></pre>
  
  <p>It keeps on giving me the same error of Attribute error list object has no attribute lstrip 
  the following is the error, stack trace :</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;pyshell#8&gt;", line 1, in &lt;module&gt;
      execfile('C:\important\secret_file.pyw')
    File "C:\important\secret_file.pyw", line 45, in &lt;module&gt;
      session.sendmail(sender,receiver,msg.as_string())
    File "C:\Python27\lib\email\message.py", line 137, in as_string
      g.flatten(self, unixfrom=unixfrom)
    File "C:\Python27\lib\email\generator.py", line 83, in flatten
      self._write(msg)
    File "C:\Python27\lib\email\generator.py", line 115, in _write
      self._write_headers(msg)
    File "C:\Python27\lib\email\generator.py", line 164, in _write_headers
      v, maxlinelen=self._maxheaderlen, header_name=h).encode()
    File "C:\Python27\lib\email\header.py", line 410, in encode
      value = self._encode_chunks(newchunks, maxlinelen)
    File "C:\Python27\lib\email\header.py", line 370, in _encode_chunks
      _max_append(chunks, s, maxlinelen, extra)
    File "C:\Python27\lib\email\quoprimime.py", line 97, in _max_append
      L.append(s.lstrip())
  AttributeError: 'list' object has no attribute 'lstrip'
  </code></pre>
  
  <p>Please Help. </p>