You have the same problem of space/tabs in all other languages, except there is no error and it can silently mislead you in badly understanding code, or just make it harder to read for hours on big project created by several generations of dev.
So Python has ... nothing. I program a lot in Python but this is one headache I could have done without. It also always makes me read a little bit further than I have to when looking at some block of code because you never know that something else might follow until you drop that indentation level back down. So now you have to count indentation levels.
And in many languages, those are optional in certain contexts (as someone else mentioned: see heartbleed).
if (a == b)
do_this()
and_always_dothis()
Who exactly considered it a bad idea and why?