Possibly due to all the sys.executable hoops that might hurt more than they help. Calling sys.executable directly for python should work: https://cs.chromium.org/search/?q=subprocess.*sys.executable&p=1&sq=package:chromium&type=cs

ckitagawa: ping?

Just I just saw this sorry I've been logged into my other account. I'll revert and investigate.

Correction: First going to try the solution thakis@ suggested since reverting has merge conflicts.

https://chromium-review.googlesource.com/c/chromium/src/+/1072159

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee3c0b0a933b9d9466620186bfeff8f62ea0af5f

commit ee3c0b0a933b9d9466620186bfeff8f62ea0af5f
Author: Calder Kitagawa <ckitagawa@chromium.org>
Date: Thu May 24 18:37:44 2018

[Zucchini] Fix ToTWinCFI

This is an attempted fix for ToTWinCFI. Looks like sys.executable logic
isn't working well on some Python configurations so directly using
sys.executable.

If this doesn't fix ToTCFI I'll revert the previous change until I can
determine what is happening:

https://chromium.googlesource.com/chromium/src/+/8e7c08d3d11c61d08ad05d3ebc283aa2d6bf7c91

Thanks to thakis@ for solution suggestion.

Bug: 844826
Change-Id: Ie1cb36fe19401e954cb84bc905cd95c9eefa1622
Reviewed-on: https://chromium-review.googlesource.com/1072159
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561567}
[modify] https://crrev.com/ee3c0b0a933b9d9466620186bfeff8f62ea0af5f/components/zucchini/fuzzers/generate_fuzzer_data.py

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/77d87185250262afe6e43367fd2d95aef5eb186e

commit 77d87185250262afe6e43367fd2d95aef5eb186e
Author: Calder Kitagawa <ckitagawa@chromium.org>
Date: Thu May 24 21:36:47 2018

[Zucchini] Disable FilePair related fuzzers on Windows

zucchini_raw_apply_seed is failing on ToTWinCFI this disables building
the target on Windows. A first attempt at a fix failed so until a better
method of diagnosing the problem is determined we will disable it as it
wasn't used by ClusterFuzz anyway (Linux only).

Bug: 844826
Change-Id: I47820432ddb94334006ee727120a242684152b97
Reviewed-on: https://chromium-review.googlesource.com/1072506
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Reviewed-by: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561641}
[modify] https://crrev.com/77d87185250262afe6e43367fd2d95aef5eb186e/components/zucchini/BUILD.gn
[modify] https://crrev.com/77d87185250262afe6e43367fd2d95aef5eb186e/components/zucchini/fuzzers/BUILD.gn

This still appears to be failing with the first change:
https://ci.chromium.org/buildbot/chromium.clang/ToTWinCFI64/1253

There isn't enough log information on LogDog to debug so I've just landed a CL to disable building this on Windows for now. ClusterFuzz infra only runs on Linux as of present anyways.  

I'd like to eventually get this to work on Windows for local development. Is there a way to run this particular buildbot configuration locally to aid in debugging?

CC: huangs@

@ckitagawa, what exactly did you mean by "run this particular buildbot configuration locally"? Running the same build with the same gn.args? You can find those in the output of the generate_build_files build step: https://logs.chromium.org/v/?s=chromium%2Fbb%2Fchromium.clang%2FToTWinCFI64%2F1253%2F%2B%2Frecipes%2Fsteps%2Fgenerate_build_files%2F0%2Fstdout

@inglorion I was referring mainly to the Python environment since that is probably the root cause of the issue... I'll try it out with those gn args to double check though.