Can't Add these plugin

[sanjaymobpair]

here is log :
(node:4006) UnhandledPromiseRejectionWarning: CordovaError: Failed to fetch plugin https://github.com/usefulio/cordova-example-plugin.git via registry.
Probably this is either a connection problem, or plugin spec is incorrect.
Check your connection and plugin name/version/URL.
Error: npm: Command failed with exit code 1 Error output:
npm ERR! premature close

npm ERR! A complete log of this run can be found in:
npm ERR! /Users/sanjaychaudhary/.npm/_logs/2018-06-04T11_28_42_496Z-debug.log
at /usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/plugman/fetch.js:173:37
at _rejected (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:864:24)
at /usr/local/lib/node_modules/cordova/node_modules/q/q.js:890:30
at Promise.when (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:1142:31)
at Promise.promise.promiseDispatch (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:808:41)
at /usr/local/lib/node_modules/cordova/node_modules/q/q.js:624:44
at runSingle (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:137:13)
at flush (/usr/local/lib/node_modules/cordova/node_modules/q/q.js:125:13)
at process._tickCallback (internal/process/next_tick.js:61:11)
(node:4006) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:4006) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.