DevTools failed to load SourceMap: Could not load content for chrome-extension://hnmpcagpplmpfojmgmnngilcnanddlhb/browser-polyfill.min.js.map: HTTP error: status code 404, net::ERR_UNKNOWN_URL_SCHEME code example

Example 1: DevTools failed to load SourceMap: Could not load content for bootstrap.min.css.map

Delete /*# sourceMappingURL=bootstrap.min.css.map */ in css/bootstrap.min.css
and delete /*# sourceMappingURL=bootstrap.css.map */ in css/bootstrap.css

It is working for me.
I hope it will work for you also.
Namaste _/\_

Example 2: DevTools failed to load SourceMap: Could not load content for

Open Developer Tools, 
go to "Settings" for Developer Tools, 
then uncheck Enable JavaScript Sourcemaps under the "Sources" settings.
Restart Browser if needed

Example 3: DevTools failed to load SourceMap: Could not load content for chrome-extension

DevTools failed to load SourceMap: Could not load content for 
chrome-extension://lhdoppojpmngadmnindnejefpokejbdd/browser-polyfill.js.map

Example 4: DevTools failed to load SourceMap: Could not load content for http://127.0.0.1:8000/bootstrap-select.min.js.map:

You need to go into Dev Tools settings and you need to unckeck 
"Enable JavaScript source maps"
"Enable CSS source maps"