<not true> At first, tests do not need global variables, there could be instance variables (self.cert and self.newcert) </not true> (read comments)

test_0006_service_show uses global cert and then the cert is used in iteration, what means that cert variable is updated several times without any guarantee which value is the last.

certs_encoded = (base64.b64encode(cert) for cert in res['usercertificate'])

See example bellow:

In [1]: cert = 1

In [2]: def f():
   ...:     global cert
   ...:     l = [cert for cert in range(4)]
   ...:     print cert
   ...:

In [3]: f()
3

In [4]: cert
Out[4]: 3

Now it accidentally works, but any change to test may cause "nice to debug" issues.

This blocks enabling of pylint check global-variable-not-assigned