Confirmed, thanks for reporting. I think that the pep8 dependency was supposed to be satisfied by webkitpy/thirdparty/pep8.py.

Invoking it without vpython (with `python format-webkitpy`) works. So after vpython I think we need to change it to explicitly change sys.path to get that dependency?

https://chromium-review.googlesource.com/c/chromium/src/+/638693

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ef32c4ae540cb5cf1be5117f9a800389cfa4864d

commit ef32c4ae540cb5cf1be5117f9a800389cfa4864d
Author: Quinten Yearsley <qyearsley@google.com>
Date: Mon Aug 28 22:46:19 2017

In formatter/main.py change sys.path so that pep8 can be found

Bug:  759231 
Change-Id: I93ec80617bd361d444c5bd6a05e3a497666c6cce
Reviewed-on: https://chromium-review.googlesource.com/638693
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>
Reviewed-by: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497914}
[modify] https://crrev.com/ef32c4ae540cb5cf1be5117f9a800389cfa4864d/third_party/WebKit/Tools/Scripts/webkitpy/common/path_finder.py
[modify] https://crrev.com/ef32c4ae540cb5cf1be5117f9a800389cfa4864d/third_party/WebKit/Tools/Scripts/webkitpy/formatter/main.py

Thanks for the quick fix!

I'm a bit confused... if this is using vpython, why didn't we add pep8 to the vpython spec?

Changing sys.path leads to the dark side of the force (most of the time :)).

:-) That's true.

My excuse/rationale here was that pep8 is used only for this script, so it doesn't quite seem right to put it in Tools/Scripts/common.vpython -- and pep8.py is already in webkitpy/thirdparty/.

Do you still think it's better to use vpython to get it? I could put a venv config inside of a comment in Tools/Scripts/format-webkitpy, right?

Ideally we'd have a common set of packages that we added and used chromium-wide and then we'd get rid of the individually hand-managed packages that have been checked in (like the ones in webkitpy/thirdparty).

Right, that's true.

I'll close this bug for now; tweaking the code to use the copy of pep8 in webkitpy/thirdparty was just keeping the status quo; it's worth noting that in general in the future we can decrease the number of checked-in dependencies.