Bug 1372127 - fix local-gen in clang-format docker image, r=me

--HG--
extra : amend_source : c6f89a38de0bbc70d2bd710f9d191335ef513c4d

automation/clang-format/setup.sh

@@ -13,6 +13,7 @@ apt_packages+=('curl')
 apt_packages+=('xz-utils')
 apt_packages+=('mercurial')
 apt_packages+=('git')
+apt_packages+=('locales')
 apt-get install -y --no-install-recommends ${apt_packages[@]}
 
 # Download clang.