Port tools/*.py to python 3

[ry]

Must continue run on python 2.7

[mreinstein]

would it be better to wait until v8's build process uses py 3? This just seems like a minefield.

[hayd]

For now an alternative, see #475, is to have python 3 error out immediately and explicitly (rather than implicitly with a SyntaxError, either in deno or later).

Going forward, would the idea be to fork/port the third_party scripts? That's a lot of code so this may be non-trivial, but we can give it a try (e.g. see how close futurize is from "just work"ing).

Note: In my first run in python 2 Luci errored because it was unable to parse the version of my default python (anaconda). So that may also have to be addressed/fixed. See also issue/below it. Probably ought to be separate issue.

[mreinstein]

2.7 is a hard requirement for building v8. It just seems like a headache to have to maintain 2 versions of python just so we can say we are on 3.

would the idea be to fork/port the third_party scripts?

That would be super painful to have to do. :(

Has anyone gauged interest within the chrome team in updating v8's build tooling py 2.7 -> 3? Assuming they are open to this that would be much nicer in that everyone shares the benefit and we don't have to maintain our own build tooling with deno's very limited resources.

[ry]

I agree with @mreinstein - forking/porting the third_party scripts is well beyond our capacity.
py3 will not be supported. When I created this issue, I mistakenly thought that the python used by the build system was included as a binary in third_party, and that we could get away with just porting our frontend scripts.

I think @hayd's solution is good - but it actually introduces some complexity for a friendly error message. If people don't understand py2 vs py3 error messages, they shouldn't be building deno in the first place. Therefore we will leave it as is.

Thanks @haoxli @hayd for the effort.

[hayd]

xlink: nodejs/node#24512

Will be interesting to see if efforts to port chromium/v8 scripts to python 3 gain any traction now EOL is < 1 year away...

[ccouzens]

It will become difficult to have the default python be 2.7 in the future.

I worked around this by creating a file bin/python.

#!/usr/bin/env bash

exec python2.7 "$@"

Making it executable chmod +x bin/python.

And sticking it in the path when running the tests: PATH="$(pwd)/bin:$PATH" cargo test.