devtools failed to load sourcemap could not load content for bootstrap.min.css.map 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: adminlte.min.css.map error

Source map files, like bootstrap.min.css.map, are generated automatically during files minification/compiling process. They actually are not needed for the production, but at the same time occupy 3 times more disk space than ones which they are mapping.
If you want just to remove that message, you can either remove comments like /*# sourceMappingURL=bootstrap.min.css.map */ in bootstrap.min.css, bootstrap.min.js, popper.min.js or any other ccs file in which you are getting error.

Example 3: 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 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"