title: google spreadsheets gspread append_row issue
body: <p>I'm working on a program that generates a dynamic google spreadsheet report.</p>
  
  <p>Sometimes when I create a new row (with data) in google spreadsheet using gspread <em>append_row</em> function it doesn't work as expected and no exception is thrown. The new line is added but there is no data inside.</p>
  
  <p>example code below:</p>
  
  <pre><code>#!/usr/bin/python
  import gspread
  
  # report line data
  report_line = ['name', 'finished &lt;None or int&gt;', 'duration &lt;str&gt;', 'id']
  
  connection = gspread.login('email@google.com', 'password')
  spreadsheet = connection.open('report_name')
  sheet = spreadsheet.sheet1
  sheet.append_row(report_line)
  </code></pre>
  
  <p>Am I missing something? Is this a known issue?
  How can I be certain that the append_row function completes successfully?</p>