kiji-schema-shell: DDLSHELL-67. Print a better exception when a Kiji cannot be opened.

issue: https://jira.kiji.org/browse/DDLSHELL-67
review: https://review.kiji.org/r/1779
commit: https://github.com/kijiproject/kiji-schema-shell/commit/551bed607d9b198c73a053f5cd7fd24020615ea3