There is two things to consider. First, API changes have been made, and one of the decisions was to remove the register_module() and unregister_module() convenience functions. The code below is an excerpt from the more detailed Release Notes of Blender 2.80 (https://wiki.blender.org/wiki/Reference/Release_Notes/2.80/Python_API/Addons#Registration):
classes = (
FooClass,
BarClass,
BazClass,
)
def register():
from bpy.utils import register_class
for cls in classes:
register_class(cls)
def unregister():
from bpy.utils import unregister_class
for cls in reversed(classes):
unregister_class(cls)
Second, the INFO_MT_file_export has been moved to TOPBAR_MT_file_export. So your code should be this in the end:
__classes__ = (
list_of_classes_you_have
)
def register():
for c in __classes__:
bpy.utils.register_class(c)
bpy.types.TOPBAR_MT_file_export.append(menu_func_export)
def unregister():
for c in reversed(__classes__):
bpy.utils.unregister_class(c)
bpy.types.TOPBAR_MT_file_export.remove(menu_func_export)
if __name__ == "__main__":
register()