Errors in n lists, ignoring duplicates in individual lists

errorlist.py

allServers = {}
finalList = []
serverErrors = []

serverErrors.append(['Error1','Error2','Error3','Error1'])
serverErrors.append(['Error3','Error2'])
serverErrors.append(['Error2','Error2','Error3','Error1','Error1','Error1','Error1'])

i = 0
for thisServerErrors in serverErrors:
	i = i + 1 
	for thisServerError in thisServerErrors:
		if not allServers.has_key(thisServerError): 
			allServers[thisServerError] = 0
		if allServers[thisServerError] == i - 1:
			allServers[thisServerError] = allServers[thisServerError] + 1

errorListLen = len(serverErrors)
for key in allServers.keys():
	if allServers[key] == errorListLen:
		finalList.append(key)

del(serverErrors)
del(allServers)

print finalList