Dropdown width over-/underflow

[Ra1ningSn0w]

Prerequisites

• [x] I have searched for similar issues in both open and closed tickets and cannot find a duplicate
• [ ] The issue still exists against the latest master branch of Select2 (not tested)
• [x] This is not a usage question (Those should be directed to the community)
• [x] I have attempted to find the simplest possible steos to reproduce the issue
• [ ] I have included a failing test as a pull request (Optional)

  Steps to reproduce the issue

  1. Create a horizontal boostrap form with a select input inside a div-tag with col-md-x option
  2. Open select input

     Expected behavior and actual behavior

When I follow those steps, I see... a 1-pixel width under-/overflow

I was expecting... no under-/overflow

Environment

Browsers

• [x] Google Chrome
• [x] Mozilla Firefox
• [x] Internet Explorer
• [x] Microsoft Edge

Operating System

• [x] Windows
• [ ] Mac OS X
• [ ] Linux
• [ ] Mobile

Libraries

• jQuery version: 2.2.0
• Select2 version: 4.0.1
• Bootstrap version: 3.3.6
• Bootstrap-Theme version: master

  Isolating the problem

• [x] This bug happens on the examples page (see col-md-3)
• [x] The bug happens consistently across all tested browsers
• [x] This bug happens when using Select2 without other pluigns
• [ ] I can reproduce this bug in a jsbin

  Example

[kevin-brown]

This is a cross-repository duplicate of https://github.com/select2/select2/issues/4224.