Python 2 scripting on Unix was great! Python just adopted the Unix tradition of pretending everything is ASCII up until it isn't, and then breaking horribly. And then the Linux world said "just use UTF-8 everywhere!" and really meant "just keep assuming things are ASCII, or at least one byte per code point, and break horribly when it isn't!"

This was great for people writing command-line scripts and utilities. This was a nightmare for people working in domains like web development.

Python 3 flipped the script: now, the string type is Unicode, and a lot of APIs broke immediately under Python 3 due to the underlying Unix environment being, well, kind of a clusterfuck when it came to locales and character encoding and hidden assumptions about ASCII or one-byte-per-character. Suddenly, all those people who had been using Python 2 -- which mostly worked identically to the way popular Linux distros did -- were using Python 3 and discovering the hell of character encoding that everybody else had been living in, and they complained loudly about it.

But for growing from a Unix-y scripting language into a general-purpose language, this change was absolutely necessary. Programmers should have to think about character encoding at their input/output boundaries, and in a high-level language should not be thinking of text as a sequence of bytes. But this requires some significant changes to how you write things like command-line utilities.

This is an example of a "yes" to one group being a "no" to another group. Or, at least, of it feeling that way.

Also, saying that Python was a great Unix-y language is not equivalent to "Python only ran on Unix and never supported Windows at all", and you know that, so it was kind of dishonest of you to try to start an argument from the assumption that I said the latter when really I said the former. Don't do that again, please.

The gain was that for everyone else (read: web, non-English, anywhere where unicode is common), python became much easier to use. But for those specific english-unix-ascii cases, it was a mild inconvenience.

Edit: as ubernostrum pointed out, more than a mild inconvenience if you were porting code. If writing new code, it was not much worse, but porting was absolutely a pain.