Gitlab-runner exec fails for invalid value of integer variable

Summary

gitlab-runner exec jobs to build local, we find gitlab-runner raise an fatal message: FATAL:invalid value for variable "MYSQL_ROOT_PASSWORD"

Steps to reproduce

gitlab-runner exec docker/shell jobname

gitlab-runner exec shell code-build
Runtime platform                                    arch=amd64 os=linux pid=25849 revision=fa86510e version=11.9.2
WARNING: You most probably have uncommitted changes.
WARNING: These changes will not be tested.
FATAL: invalid value for variable "MYSQL_ROOT_PASSWORD"

.gitlab-ci.yml

variables:
  DOCKER_USER: abc
  DOCKER_PASSWORD: abc
  MYSQL_DATABASE: software
  MYSQL_ROOT_PASSWORD: 123456

Actual behavior

Gitlab-runner exec Job succeeds only when change 123456 to a123456. While gitlab-CI pipeline executes well both, so I guess it should be the bug of the gitlab-runner exec part.

Edited May 29, 2019 by Deepglint