You can get this error after 2015-11-23 update:
https://github.com/magento/magento2/commit/066d510d2d83650befdbec809755d2e29006c862
Now the following syntax is wrong:
bin/magento i18n:collect-phrases -o "C:/work/mage2.pro/store/app/i18n/df/ru_ru/dictionary-2.csv" -m "C:/work/mage2.pro/store"
You shold write or
bin/magento i18n:collect-phrases -o "C:/work/mage2.pro/store/app/i18n/df/ru_ru/dictionary-2.csv" -m
either
bin/magento i18n:collect-phrases -o "C:/work/mage2.pro/store/app/i18n/df/ru_ru/dictionary-2.csv" "C:/work/mage2.pro/store"
The -m case means that Magento 2 should parse all its files.
The second case (without -m) means that Magento 2 should parse only the directory specified.