Update do-not-strip-path explanation. There is a common trap.

slapos.extension.strip_/README.rst

@@ -50,11 +50,13 @@ Supported Options
 ``do-not-strip-path``
 
   A new-line separated list of absolute paths of the files you do not
-  want to strip.
+  want to strip. Do not refer a section to get its location. If you do
+  like ${bazel:location}/bin/bazel, buildout will not work correctly.
+  Instead do like ${buildout:parts-directory}/bazel/bin/bazel.
 
   An example::
 
     [buildout]
     do-not-strip-path =
-      ${bazel:location}/bin/bazel
-      ${another-part:location}/bin/dontstripbinary
+      ${buildout:parts-directory}/bazel/bin/bazel
+      ${buildout:parts-directory}/anotherparts/bin/dontstripbinary