In the case of a single element tuple, the trailing comma is required.
a = ('foo',)
a = ('foo1', 'foo2')
b = ('foo1', 'foo2',)
In all cases except the empty tuple the comma is the important thing. Parentheses are only required when required for other syntactic reasons: to distinguish a tuple from a set of function arguments, operator precedence, or to allow line breaks.
The trailing comma for tuples, lists, or function arguments is good style especially when you have a long initialisation that is split over multiple lines. If you always include a trailing comma then you won't add another line to the end expecting to add another element and instead just creating a valid expression:
a = [ "a", "b" "c" ]
Assuming that started as a 2 element list that was later extended it has gone wrong in a perhaps not immediately obvious way. Always include the trailing comma and you avoid that trap.