rhn_register: fix broken imports, add unit tests (#26878)

Fix 'module' object is not callable

* rhn_register: fix Python 3 compatibility
* rhn_register: update requirements
* rhn_register: add unit tests
* Add missing method name
* use a dedicated line for XML related requirements
* rhn_register: drop support for Python 2.4
* rhn_register unit tests: fix Python 3 compatibility
* refactor in order to check order of the requests

lib/ansible/modules/packaging/os/rhn_register.py

@@ -27,6 +27,7 @@ notes:
     - In order to register a system, rhnreg_ks requires either a username and password, or an activationkey.
 requirements:
     - rhnreg_ks
+    - either libxml2 or lxml
 options:
     state:
         description:
@@ -132,8 +133,6 @@ RETURN = '''
 
 import os
 import sys
-import urlparse
-import xmlrpclib
 
 # Attempt to import rhn client tools
 sys.path.insert(0, '/usr/share/rhn')
@@ -146,7 +145,8 @@ except ImportError:
 
 # INSERT REDHAT SNIPPETS
 from ansible.module_utils import redhat
-from ansible.module_utils.basic import AnsibleModule, get_exception
+from ansible.module_utils.basic import AnsibleModule
+from ansible.module_utils.six.moves import urllib, xmlrpc_client
 
 
 class Rhn(redhat.RegistrationBase):
@@ -184,7 +184,7 @@ class Rhn(redhat.RegistrationBase):
 
             Returns: str
         '''
-        url = urlparse.urlparse(self.server_url)
+        url = urllib.parse.urlparse(self.server_url)
         return url[1].replace('xmlrpc.', '')
 
     @property
@@ -283,7 +283,7 @@ class Rhn(redhat.RegistrationBase):
                 url = "https://%s/rpc/api" % self.hostname
             else:
                 url = "https://xmlrpc.%s/rpc/api" % self.hostname
-            self.server = xmlrpclib.Server(url, verbose=0)
+            self.server = xmlrpc_client.ServerProxy(url)
             self.session = self.server.auth.login(self.username, self.password)
 
         func = getattr(self.server, method)
@@ -396,9 +396,8 @@ def main():
             rhn.enable()
             rhn.register(enable_eus, activationkey, profilename, sslcacert, systemorgid)
             rhn.subscribe(channels)
-        except Exception:
-            e = get_exception()
-            module.fail_json(msg="Failed to register with '%s': %s" % (rhn.hostname, e))
+        except Exception as exc:
+            module.fail_json(msg="Failed to register with '%s': %s" % (rhn.hostname, exc))
         finally:
             rhn.logout()
 
@@ -411,9 +410,8 @@ def main():
 
         try:
             rhn.unregister()
-        except Exception:
-            e = get_exception()
-            module.fail_json(msg="Failed to unregister: %s" % e)
+        except Exception as exc:
+            module.fail_json(msg="Failed to unregister: %s" % exc)
         finally:
             rhn.logout()