i ran punjab - BOSH connection manager - using twistd -y punjab.tac command in my centos but i am getting following error

Unhandled Error
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/twisted/application/app.py", line 652, in run
    runApp(config)
  File "/usr/local/lib/python2.7/site-packages/twisted/scripts/twistd.py", line 23, in runApp
    _SomeApplicationRunner(config).run()
  File "/usr/local/lib/python2.7/site-packages/twisted/application/app.py", line 386, in run
    self.application = self.createOrGetApplication()
  File "/usr/local/lib/python2.7/site-packages/twisted/application/app.py", line 451, in createOrGetApplication
    application = getApplication(self.config, passphrase)
--- <exception caught here> ---
  File "/usr/local/lib/python2.7/site-packages/twisted/application/app.py", line 462, in getApplication
    application = service.loadApplication(filename, style, passphrase)
  File "/usr/local/lib/python2.7/site-packages/twisted/application/service.py", line 405, in loadApplication
    application = sob.loadValueFromFile(filename, 'application', passphrase)
  File "/usr/local/lib/python2.7/site-packages/twisted/persisted/sob.py", line 210, in loadValueFromFile
    exec fileObj in d, d
  File "punjab.tac", line 39, in <module>
    '/etc/pki/tls/cert.pem',
  File "/usr/local/lib/python2.7/site-packages/twisted/internet/ssl.py", line 68, in __init__
    self.cacheContext()
  File "/usr/local/lib/python2.7/site-packages/twisted/internet/ssl.py", line 78, in cacheContext
    ctx.use_privatekey_file(self.privateKeyFileName)
OpenSSL.SSL.Error: [('x509 certificate routines', 'X509_check_private_key', 'key values mismatch')]

Failed to load application: [('x509 certificate routines', 'X509_check_private_key', 'key values mismatch')]

my configuration file of punjab is

sslContext = ssl.DefaultOpenSSLContextFactory(

        '/etc/pki/tls/private/ca.key',
        '/etc/pki/tls/cert.pem',
)

How can i resolve above error