See the log on chrotomation2.
/usr/local/google2/crostc/buildbot_tester.peppy.295217,315731.Tue.out 

OUTPUT: Preparing to download control_files.tar package to local directory.
OUTPUT: CMD: gsutil cp gs://chromeos-image-archive/peppy-chrome-pfq/R56-8991.0.0-rc1/control_files.tar /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; tar -xvf  autotest_packages.tar
(Uncompressing autotest file autotest_packages.tar .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; rm -f autotest_packages.tar
(Removing processed autotest file autotest_packages.tar .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; tar -jxvf  autotest_server_package.tar.bz2
(Uncompressing autotest file autotest_server_package.tar.bz2 .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; rm -f autotest_server_package.tar.bz2
(Removing processed autotest file autotest_server_package.tar.bz2 .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; tar -xvf  control_files.tar
(Uncompressing autotest file control_files.tar .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; rm -f control_files.tar
(Removing processed autotest file control_files.tar .)
OUTPUT: CMD: cd /tmp/peppy-chrome-pfq/R56-8991.0.0-rc1 ; mv autotest autotest_files
(Moving downloaded autotest files to autotest_files)
OUTPUT: Acquiring checksum for 'nonafdo_image'.
df6af0887b895ae968b3421207c13e03  /usr/local/google2/crostc/chromeos/chroot/tmp/peppy-chrome-pfq/R56-8991.0.0-rc1/chromiumos_test_image.bin
OUTPUT: Computed checksum is : df6af0887b895ae968b3421207c13e03
OUTPUT: Checksum is: df6af0887b895ae968b3421207c13e03
OUTPUT: Preparing to download trybot-peppy-release/R56-8992.0.0-b7189 image to local directory.
OUTPUT: CMD: gsutil cp gs://chromeos-image-archive/trybot-peppy-release/R56-8992.0.0-b7189/chromiumos_test_image.tar.xz /tmp/trybot-peppy-release/R56-8992.0.0-b7189
OUTPUT: CMD: cd /tmp/trybot-peppy-release/R56-8992.0.0-b7189 ; tar -Jxf chromiumos_test_image.tar.xz
(Uncompressing and un-tarring may take a couple of minutes...please be patient.)
OUTPUT: CMD: cd /tmp/trybot-peppy-release/R56-8992.0.0-b7189 ; rm -f chromiumos_test_image.tar.xz;
(Removing file chromiumos_test_image.tar.xz.)
OUTPUT: Using image from /usr/local/google2/crostc/chromeos/chroot/tmp/trybot-peppy-release/R56-8992.0.0-b7189/chromiumos_test_image.bin.
Crosperf error: MissingFile('Cannot find autotest package file: autotest_packages.tar.',)
Traceback (most recent call last):
  File "./buildbot_test_toolchains.py", line 392, in <module>
    retval = Main(sys.argv)
  File "./buildbot_test_toolchains.py", line 388, in Main
    return fc.DoAll()
  File "./buildbot_test_toolchains.py", line 330, in DoAll
    self._TestImages(trybot_image, vanilla_image, nonafdo_image)
  File "./buildbot_test_toolchains.py", line 229, in _TestImages
    raise RuntimeError('Crosperf execution error!')
RuntimeError: Crosperf execution error!