Assertion tweak for typo.
Assertion tweak for typo.

BUG=None
TEST=unittests, manual, pylint.

Change-Id: I07ce916d19e458683f18fa30ada0780c83d03ffc
Reviewed-on: https://gerrit.chromium.org/gerrit/27851
Reviewed-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>
Tested-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

zhang0137/chromite,zhang0137/chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,coreos/chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite