gistfile1.py

#!/usr/bin/env python

import gzip
try:
    import cStringIO as StringIO
except:
    import StringIO

# ...

@app.route('/cas/<cas_id>')
@login_required
def cas(cas_id):
    # ...

    try:
        string_io = StringIO.StringIO()
        string_io.write(cas_gzipped)
        f = gzip.open(fileobj=string_io, 'rb')
        xmi = f.read()
    except:
        error_msg = 'There was an error in decompressing the CAS'
        return render_template('error.html', error_msg=error_msg)

    # ...