[vpython] Update vpython

From https://chromium.googlesource.com/infra/luci/luci-go:
git log a90d36d07f65098da34b600f6cfb8a5f05199ac5..63bd11762eec0b8604bc89dcfb9de4f5dad3777a --oneline vpython

e638db97 [vpython] Normalize spec before verification.
22c141ce [vpython] Remove maximum script path length check.
b1e7bc36 [vpython] Better failure output.
3edc75c8 [vpython] Better VirtualEnv isolation.

R=dnj@chromium.org, nodir@chromium.org

Bug:
Change-Id: I20d06c51760b27e70b9ce65c7ddd856943fab7eb
Reviewed-on: https://chromium-review.googlesource.com/731512Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Robbie Iannucci <iannucci@chromium.org>

cipd_manifest.txt

@@ -2,8 +2,13 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+$VerifiedPlatform linux-386 linux-amd64 linux-arm64 linux-armv6l linux-mips64
+$VerifiedPlatform linux-ppc64 linux-ppc64le linux-s390x
+$VerifiedPlatform mac-amd64
+$VerifiedPlatform windows-386 windows-amd64
+
 # vpython.
-infra/tools/luci/vpython/${platform}  git_revision:d1e9a52e1c8414cd0a0df8bec6c37f325e0fbaa1
+infra/tools/luci/vpython/${platform}  git_revision:a3d636052088db3daa48413b3e209eed4f5cb4ad
 
 # LUCI editor
 infra/tools/luci/led/${platform}  git_revision:d1e9a52e1c8414cd0a0df8bec6c37f325e0fbaa1