title: ValueError: unsupported format character '}' when use % string formatting
body: <p>I'm trying to generate some LaTeX markup by using Python % string formatting.  I use named fields in the string and use a dictionary with matching keys for the data.  However, I get the error <code>ValueError: unsupported format character '}'</code>.  Why isn't this code working?</p>
  
  <pre><code>LaTeXentry = '''\\subsection{{%(title)}}
      \\begin{{itemize}}
      \\item 
      %(date)
      \\item
      %(description)
      \\item
      Source:\\cite{{%(title)}}
      \\item
      filename(s):
      %(filename)
      \\item 
      Contributed by %(name)'''
  
  LaTeXcodeToAdd = LaTeXentry % {
      "time" : Timestamp,
      "date" : date,
      "description" : summary, 
      "filename" : filename,
      "name" : name,
      "title": title,
  }
  </code></pre>
  
  
  
  <pre><code>Traceback (most recent call last):
    File "file_directory", line 115, in &lt;module&gt;
      "title": title,
  ValueError: unsupported format character '}' (0x7d) at index 21
  </code></pre>