Hi, I just installed this package using the following command :

sebastien@computer:~$ wp package install git@github.com:wp-cli/i18n-command.git
Installing package wp-cli/i18n-command (dev-master)
Updating /home/sebastien/.wp-cli/packages/composer.json to require the package...
Registering git@github.com:wp-cli/i18n-command.git as a VCS repository...
Using Composer to install the package...
---
Loading composer repositories with package information
Updating dependencies
Resolving dependencies through SAT
Dependency resolution completed in 0.630 seconds
Analyzed 5408 packages to resolve dependencies
Analyzed 311465 rules to resolve dependencies
Package operations: 3 installs, 0 updates, 0 removals
Installs: gettext/languages:2.3.0, gettext/gettext:v4.4.3, wp-cli/i18n-command:dev-master 93c1109

• Installing gettext/languages (2.3.0)
• Warning: gettext/gettext v4.4.3 requires gettext/languages ^2.3 -> satisfiable by gettext/languages[2.3.0].
• Installing gettext/gettext (v4.4.3)
• Warning: wp-cli/i18n-command dev-master requires gettext/gettext ^4.4 -> satisfiable by gettext/gettext[v4.4.0, v4.4.1, v4.4.2, v4.4.3].
• Installing wp-cli/i18n-command (dev-master 93c1109)
  Writing lock file
  Generating autoload files
  ---
  Success: Package installed.

But when I want to use it, I got this error message :

sebastien@computer:~$ wp i18n
Error: Callable "\WP_CLI\I18n\Command_Namespace" does not exist, and cannot be registered as wp i18n.

Here the tree of my .wp-cli folder :

sebastien@computer:~$ find .wp-cli -type d
.wp-cli
.wp-cli/packages
.wp-cli/packages/vendor
.wp-cli/packages/vendor/bin
.wp-cli/packages/vendor/wp-cli
.wp-cli/packages/vendor/wp-cli/i18n-command
.wp-cli/packages/vendor/wp-cli/i18n-command/.git
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/info
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs/refs
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs/refs/heads
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs/refs/remotes
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs/refs/remotes/origin
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/logs/refs/remotes/composer
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/branches
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs/tags
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs/heads
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs/remotes
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs/remotes/origin
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/refs/remotes/composer
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/objects
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/objects/pack
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/objects/info
.wp-cli/packages/vendor/wp-cli/i18n-command/.git/hooks
.wp-cli/packages/vendor/wp-cli/i18n-command/features
.wp-cli/packages/vendor/wp-cli/i18n-command/features/steps
.wp-cli/packages/vendor/wp-cli/i18n-command/features/extra
.wp-cli/packages/vendor/wp-cli/i18n-command/features/bootstrap
.wp-cli/packages/vendor/wp-cli/i18n-command/src
.wp-cli/packages/vendor/wp-cli/i18n-command/bin
.wp-cli/packages/vendor/wp-cli/i18n-command/utils
.wp-cli/packages/vendor/wp-cli/i18n-command/.github
.wp-cli/packages/vendor/gettext
.wp-cli/packages/vendor/gettext/gettext
.wp-cli/packages/vendor/gettext/gettext/.git
.wp-cli/packages/vendor/gettext/gettext/.git/info
.wp-cli/packages/vendor/gettext/gettext/.git/logs
.wp-cli/packages/vendor/gettext/gettext/.git/logs/refs
.wp-cli/packages/vendor/gettext/gettext/.git/logs/refs/heads
.wp-cli/packages/vendor/gettext/gettext/.git/logs/refs/remotes
.wp-cli/packages/vendor/gettext/gettext/.git/logs/refs/remotes/origin
.wp-cli/packages/vendor/gettext/gettext/.git/logs/refs/remotes/composer
.wp-cli/packages/vendor/gettext/gettext/.git/branches
.wp-cli/packages/vendor/gettext/gettext/.git/refs
.wp-cli/packages/vendor/gettext/gettext/.git/refs/tags
.wp-cli/packages/vendor/gettext/gettext/.git/refs/heads
.wp-cli/packages/vendor/gettext/gettext/.git/refs/remotes
.wp-cli/packages/vendor/gettext/gettext/.git/refs/remotes/origin
.wp-cli/packages/vendor/gettext/gettext/.git/refs/remotes/composer
.wp-cli/packages/vendor/gettext/gettext/.git/objects
.wp-cli/packages/vendor/gettext/gettext/.git/objects/pack
.wp-cli/packages/vendor/gettext/gettext/.git/objects/info
.wp-cli/packages/vendor/gettext/gettext/.git/hooks
.wp-cli/packages/vendor/gettext/gettext/src
.wp-cli/packages/vendor/gettext/gettext/src/Utils
.wp-cli/packages/vendor/gettext/gettext/src/Generators
.wp-cli/packages/vendor/gettext/gettext/src/Extractors
.wp-cli/packages/vendor/gettext/gettext/tests
.wp-cli/packages/vendor/gettext/gettext/tests/assets
.wp-cli/packages/vendor/gettext/gettext/tests/assets/phpcode
.wp-cli/packages/vendor/gettext/gettext/tests/assets/twig
.wp-cli/packages/vendor/gettext/gettext/tests/assets/jscode
.wp-cli/packages/vendor/gettext/gettext/tests/assets/po2
.wp-cli/packages/vendor/gettext/gettext/tests/assets/po
.wp-cli/packages/vendor/gettext/gettext/tests/assets/phpcode2
.wp-cli/packages/vendor/gettext/gettext/tests/assets/blade
.wp-cli/packages/vendor/gettext/gettext/tests/assets/po3
.wp-cli/packages/vendor/gettext/gettext/tests/assets/jscode2
.wp-cli/packages/vendor/gettext/gettext/tests/assets/phpcode3
.wp-cli/packages/vendor/gettext/gettext/tests/assets/jed
.wp-cli/packages/vendor/gettext/languages
.wp-cli/packages/vendor/gettext/languages/.git
.wp-cli/packages/vendor/gettext/languages/.git/info
.wp-cli/packages/vendor/gettext/languages/.git/logs
.wp-cli/packages/vendor/gettext/languages/.git/logs/refs
.wp-cli/packages/vendor/gettext/languages/.git/logs/refs/heads
.wp-cli/packages/vendor/gettext/languages/.git/logs/refs/remotes
.wp-cli/packages/vendor/gettext/languages/.git/logs/refs/remotes/origin
.wp-cli/packages/vendor/gettext/languages/.git/logs/refs/remotes/composer
.wp-cli/packages/vendor/gettext/languages/.git/branches
.wp-cli/packages/vendor/gettext/languages/.git/refs
.wp-cli/packages/vendor/gettext/languages/.git/refs/tags
.wp-cli/packages/vendor/gettext/languages/.git/refs/heads
.wp-cli/packages/vendor/gettext/languages/.git/refs/remotes
.wp-cli/packages/vendor/gettext/languages/.git/refs/remotes/origin
.wp-cli/packages/vendor/gettext/languages/.git/refs/remotes/composer
.wp-cli/packages/vendor/gettext/languages/.git/objects
.wp-cli/packages/vendor/gettext/languages/.git/objects/pack
.wp-cli/packages/vendor/gettext/languages/.git/objects/info
.wp-cli/packages/vendor/gettext/languages/.git/hooks
.wp-cli/packages/vendor/gettext/languages/src
.wp-cli/packages/vendor/gettext/languages/src/cldr-data
.wp-cli/packages/vendor/gettext/languages/src/cldr-data/main
.wp-cli/packages/vendor/gettext/languages/src/cldr-data/main/en-US
.wp-cli/packages/vendor/gettext/languages/src/cldr-data/supplemental
.wp-cli/packages/vendor/gettext/languages/src/Exporter
.wp-cli/packages/vendor/gettext/languages/bin
.wp-cli/packages/vendor/gettext/languages/tests
.wp-cli/packages/vendor/gettext/languages/tests/Get
.wp-cli/packages/vendor/gettext/languages/tests/Rules
.wp-cli/packages/vendor/composer