diff --git a/branches/ucs-3.2/ucs-3.2-1/base/univention-lib/python/umc_connection.py b/branches/ucs-3.2/ucs-3.2-1/base/univention-lib/python/umc_connection.py
index f22c093..0b38906 100644
--- a/branches/ucs-3.2/ucs-3.2-1/base/univention-lib/python/umc_connection.py
+++ b/branches/ucs-3.2/ucs-3.2-1/base/univention-lib/python/umc_connection.py
@@ -32,22 +32,37 @@
 # <http://www.gnu.org/licenses/>.
 
 # stdlib
-from httplib import HTTPSConnection, HTTPException
+from httplib import HTTPSConnection, HTTPException, OK as HTTP_OK, FORBIDDEN
 from json import loads, dumps
 from socket import error as SocketError
 
 # univention
 from univention.config_registry import ConfigRegistry
-ucr = ConfigRegistry()
-ucr.load()
+
+
+class UMCConnectionError(HTTPException):
+	pass
+
+
+class UMCConnectionUnknownCommand(UMCConnectionError):
+	pass
+
+
+class UMCConnectionRequestError(UMCConnectionError):
+	pass
+
+
+class UMCConnectionAuthenticationError(UMCConnectionRequestError):
+	pass
+
 
 class UMCConnection(object):
 	def __init__(self, host, username=None, password=None, error_handler=None):
 		self._host = host
 		self._headers = {
-			'Content-Type' : 'application/json; charset=UTF-8'
+			'Content-Type': 'application/json; charset=UTF-8'
 		}
-		self._error_handler=error_handler
+		self._error_handler = error_handler
 		if username is not None:
 			self.auth(username, password)
 
@@ -61,6 +76,9 @@ class UMCConnection(object):
 	def get_machine_connection(cls, error_handler=None):
 		'''Creates a connection with the credentials of the local host
 		to the DC Master'''
+		ucr = ConfigRegistry()
+		ucr.load()
+
 		username = '%s$' % ucr.get('hostname')
 		password = ''
 		try:
@@ -82,7 +100,7 @@ class UMCConnection(object):
 		'''Tries to authenticate against the host and preserves the
 		cookie. Has to be done only once (but keep in mind that the
 		session probably expires after 10 minutes of inactivity)'''
-		data = self.build_data({'username' : username, 'password' : password})
+		data = self.build_data({'username': username, 'password': password})
 		con = self.get_connection()
 		try:
 			con.request('POST', '/umcp/auth', data)
@@ -91,23 +109,23 @@ class UMCConnection(object):
 			if self._error_handler:
 				self._error_handler(str(e))
 			error_message = '%s: Authentication failed while contacting: %s' % (self._host, e)
-			raise HTTPException(error_message)
+			raise UMCConnectionAuthenticationError(error_message)
 		else:
 			try:
 				response = con.getresponse()
 				cookie = response.getheader('set-cookie')
 				if cookie is None:
-					raise ValueError('No cookie')
+					raise UMCConnectionAuthenticationError('No cookie')
 				self._headers['Cookie'] = cookie
 			except Exception as e:
 				if self._error_handler:
 					self._error_handler(str(e))
 				error_message = '%s: Authentication failed: %s' % (self._host, response.read())
-				raise HTTPException(error_message)
+				raise UMCConnectionAuthenticationError(error_message)
 
 	def build_data(self, data, flavor=None):
 		'''Returns a dictionary as expected by the UMC Server'''
-		data = {'options' : data}
+		data = {'options': data}
 		if flavor:
 			data['flavor'] = flavor
 		return dumps(data)
@@ -130,15 +148,14 @@ class UMCConnection(object):
 			umcp_command = '%s/%s' % (umcp_command, url)
 		con.request('POST', umcp_command, data, headers=self._headers)
 		response = con.getresponse()
-		if response.status != 200:
+		if response.status != HTTP_OK:  # 200
 			error_message = '%s on %s (%s): %s' % (response.status, self._host, url, response.read())
-			if response.status == 403:
+			if response.status == FORBIDDEN:  # 403
 				# 403 is either command is unknown
 				#   or command is known but forbidden
 				if self._error_handler:
 					self._error_handler(error_message)
-				raise NotImplementedError('command forbidden: %s' % url)
-			raise HTTPException(error_message)
+				raise UMCConnectionUnknownCommand('command forbidden: %s' % url)
+			raise UMCConnectionRequestError(error_message)
 		content = response.read()
 		return loads(content)['result']
-