import re

wikiText = """==Mainsection1==
Some text here
===Subsection1.1===
Other text here

==Mainsection2==
Text goes here
===Subsecttion2.1===
Other text goes here. """

outputArray = re.findall('(?<!=)==([^=]+)==(?!=)([\s\S]*?(?=$|(?<!=)==[^=]+==(?!=)))', wikiText)
print outputArray

outputArray = re.findall('(?<!=)==([^=]*)==(?!=)([^=]*)', wikiText, re.MULTILINE)
print outputArray

[('Mainsection1', '\nSome text here\n===Subsection1.1===\nOther text here\n\n'), ('Mainsection2', '\nText goes here\n===Subsecttion2.1===\nOther text goes here. ')]
[('Mainsection1', '\nSome text here\n'), ('Mainsection2', '\nText goes here\n')]