YAMLのロード時の例外捕捉

[kmuto]

YAMLエラーのときに捕捉されず最後まで例外が飛んでしまう。
config.ymlで pdfmaker: をコメントしている状態で下位の makeindex: null を有効にするとか。

$ rake pdf
review-pdfmaker  config.yml
Traceback (most recent call last):
	11: from /home/kmuto/review/bin/review-pdfmaker:14:in `<main>'
	10: from /home/kmuto/review/lib/review/pdfmaker.rb:93:in `execute'
	 9: from /home/kmuto/review/lib/review/pdfmaker.rb:124:in `execute'
	 8: from /home/kmuto/review/lib/review/configure.rb:160:in `create'
	 7: from /home/kmuto/review/lib/review/yamlloader.rb:53:in `load_file'
	 6: from /home/kmuto/review/lib/review/yamlloader.rb:9:in `safe_load_file'
	 5: from /home/kmuto/review/lib/review/yamlloader.rb:9:in `open'
	 4: from /home/kmuto/review/lib/review/yamlloader.rb:12:in `block in safe_load_file'
	 3: from /usr/lib/ruby/2.7.0/psych.rb:349:in `safe_load'
	 2: from /usr/lib/ruby/2.7.0/psych.rb:390:in `parse'
	 1: from /usr/lib/ruby/2.7.0/psych.rb:456:in `parse_stream'
/usr/lib/ruby/2.7.0/psych.rb:456:in `parse': (/tmp/a/config.yml): did not find expected key while parsing a block mapping at line 8 column 1 (Psych::SyntaxError)
	4: from /home/kmuto/review/bin/review-pdfmaker:14:in `<main>'
	3: from /home/kmuto/review/lib/review/pdfmaker.rb:93:in `execute'
	2: from /home/kmuto/review/lib/review/pdfmaker.rb:124:in `execute'
	1: from /home/kmuto/review/lib/review/configure.rb:158:in `create'
/home/kmuto/review/lib/review/configure.rb:162:in `rescue in create': yaml error (/tmp/a/config.yml): did not find expected key while parsing a block mapping at line 8 column 1 (ReVIEW::ConfigError)
rake aborted!

手前で捕捉して妥当なエラーメッセージにする。