problem
Use the source, Luke!
Have a look at the file from the error message:
if (typeof Promise === 'undefined') {
// ES6 Promise isn't supported, NodeJS is pre-0.12;
throw new TypeError("Promise library must be specified.");
}
The version of Node.js in your Ubuntu distro is very old.
solution
I'd recommend that you upgrade Node.js, use LTS version for example (4.x).
An alternative would be to specify a promise library as instructed on the project's website.
Pro-tip: nvm is a great solution to manage versions of Node.js.
update - 1
Starting from version 5.6.0 of the library, it no longer supports Node.js 0.10.x and 0.12.x, requiring Node.js 4.x as the new minimum.
As a result, that error has been depreciated, as the library will always successfully default to ES6 Promise, if you do not specify any custom promise library.
And if you try running it under Node.js prior to 4.0, it will throw Minimum Node.js version required by pg-promise is 4.x
inside its loader.
update - 2
Version 6.7.0 and later require Node.js 4.5.0 as the minimum.