This reverts commit bf26b167.

Reason for revert: spec revert for https://bugs.chromium.org/p/chromium/issues/detail?id=1025659

Original change's description:
> depot_tools: Ensure Python is bootstrapped before reading python3_bin_reldir.txt
> 
> Bug: 1017812
> Change-Id: I7013e5445ff5917fab813a54fed416d9770d2684
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1913269
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Dirk Pranke <dpranke@chromium.org>

TBR=dpranke@chromium.org,ehmaldonado@chromium.org,apolito@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1017812
Change-Id: I8e10894a2e835c20ece7d555c21f6ce1f76528a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1922949Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>