[ENOENT] Screenshot not found in right side

[branneman]

Basically, a Screenshot not found in right side error message also reports an internal error.

$ argus-eyes compare baseline current
Screenshot not found in right side: /<redacted>/.argus-eyes/current/1280x768/homepage/cms-featured-articles.png
Screenshot not found in right side: /<redacted>/.argus-eyes/current/320x480/homepage/cms-featured-articles.png

Error: ENOENT: no such file or directory, open '/<redacted>/.argus-eyes/current/1280x768/homepage/cms-featured-articles.png'
    at Error (native)
    at Object.fs.openSync (fs.js:634:18)
    at Object.fs.readFileSync (fs.js:502:33)
    at Function.PNGImage.readImageSync (/<redacted>/lib/node_modules/argus-eyes/node_modules/pngjs-image/index.js:175:31)
    at Object.BlinkDiff._loadImageSync (/<redacted>/lib/node_modules/argus-eyes/node_modules/blink-diff/index.js:685:20)
    at Object.BlinkDiff.runSync (/<redacted>/lib/node_modules/argus-eyes/node_modules/blink-diff/index.js:495:24)
    at dir1.forEach.e (/<redacted>/lib/node_modules/argus-eyes/app/action-compare.js:67:31)
    at Array.forEach (native)
    at compare (/<redacted>/lib/node_modules/argus-eyes/app/action-compare.js:49:10)
    at Object.<anonym

Image comparison returned an error for file: '1280x768/homepage/cms-featured-articles.png'
 BlinkDiff: {"errno":-2,"code":"ENOENT","syscall":"open","path":"/<redacted>/.argus-eyes/current/1280x768/homepage/cms-featured-articles.png"}
Difference (0.17%) above threshold (0%) found for: '1280x768/homepage/search-block.png'
Image comparison returned an error for file: '320x480/homepage/cms-featured-articles.png'
 BlinkDiff: {"errno":-2,"code":"ENOENT","syscall":"open","path":"/<redacted>/.argus-eyes/current/320x480/homepage/cms-featured-articles.png"}
Difference (0.27%) above threshold (0%) found for: '320x480/homepage/search-block.png'
Found 2 differences
Diff images saved in: '.argus-eyes/diff_baseline_current'