I found the /_locales/ directory in the following location:
~/Library/Caches/com.apple.Safari/Extensions/Evernote Web Clipper.safariextension/_locales
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Seems we're discussing two separate error messages in this thread... I'm not a programmer, so I've not a solid understanding of how they are connected:
#1: the error related to the language localization (original post by joeworkman)
#2: the error related to cross origin requests (added by Tschügge)
For me, duplicating the /en/ directory and renaming /en_US/ seems to work as a hack for removing the console log Errors in #1 (thanks Rodrigo Passos!).
After creating the /en_US/ directory, I then began receiving console log Warnings from BOTH /en/messages.json and /en_US/messages.json regarding insecure content.
These insecure content errors seem to trace back to a file named "port.js" and specifically to Line 152, which seems to be involved in a variable named "c" as defined:
var c = new XMLHttpRequest;
As jbignert noted, the port.js file is indeed located in the /third_party/ directory... however, the first line of port.js reads:
/*! Copyright 2009-2017 Evernote Corporation. All rights reserved. */
FWIW, a second file named jsonrpc.js located in /third_party/ also includes the above copyright notice.
