--webrtc doesn't work on OS X

~$ hyperirc --mirror=##politics --all --webrtc
Mirroring ##politics to 31b1eeb9a0350d32e90e3dfc91beb341e00aee31a313c7a6b8a0d6147b30b8aa

events.js:174
      throw er; // Unhandled 'error' event
      ^

Error: Could not start Xvfb: "Xvfb is not installed or is not in your $PATH".
The "xvfb" package is required to run "electron-eval" on Linux. Please install it first ("sudo apt-get install xvfb").
    at /usr/local/lib/node_modules/hyperirc/node_modules/electron-eval/lib/index.js:147:22
    at ChildProcess.onError (/usr/local/lib/node_modules/hyperirc/node_modules/headless/index.js:70:9)
    at Object.onceWrapper (events.js:286:20)
    at ChildProcess.emit (events.js:198:13)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:246:12)
    at onErrorNT (internal/child_process.js:415:16)
    at process._tickCallback (internal/process/next_tick.js:63:19)
Emitted 'error' event at:
    at Daemon.error (/usr/local/lib/node_modules/hyperirc/node_modules/electron-eval/lib/index.js:101:12)
    at /usr/local/lib/node_modules/hyperirc/node_modules/electron-eval/lib/index.js:56:31
    at /usr/local/lib/node_modules/hyperirc/node_modules/electron-eval/lib/index.js:148:18
    at ChildProcess.onError (/usr/local/lib/node_modules/hyperirc/node_modules/headless/index.js:70:9)
    [... lines matching original stack trace ...]
    at process._tickCallback (internal/process/next_tick.js:63:19)

Seems like electron's headless mode isn't supported on macOS

macOS version: 10.14.6
npm version: 6.11.3
node version: v10.16.0

~$ npm -g list | grep electron
│ ├─┬ electron-webrtc@0.2.12
│ │ ├─┬ electron-eval@0.9.10
│ │ │ ├─┬ electron@1.8.8
│ │ │ │ ├─┬ electron-download@3.3.0
│ │ ├── electron-to-chromium@1.3.119
  │ │ │ │ │ └── electron-to-chromium@1.3.116

Reproduce the failure with hyperirc --mirror=##politics --all --webrtc on macOS, then inspect the electron-eval and headless integration named in the stack trace. Compare the Xvfb-dependent startup path with macOS behavior and verify that the WebRTC command starts successfully without the reported error.