Merge pull request #1810 from gaurarpit/test1

Add expected error behavior into docs

Author: marioidival

CONTRIBUTING.md

@@ -53,6 +53,13 @@ $ cargo install mdbook
 $ mdbook build
 ```
 
+**The following warnings can be ignored safely.**
+
+```
+[WARN] (mdbook::preprocess::cmd): The command wasn't found, is the "gettext" preprocessor installed?
+[WARN] (mdbook::preprocess::cmd):   Command: mdbook-gettext
+```
+
 [install Rust]: http://rust-lang.org/install.html
 
 The files will be in the `book` directory at the top-level; `mdbook serve` will

README.md

@@ -27,7 +27,7 @@ mdbook serve
 To be able to run the examples, you must be connected to the internet; you can
 read all content offline, however!
 
-The following warnings can be ignored safely.
+**The following warnings can be ignored safely.**
 
 ```
 [WARN] (mdbook::preprocess::cmd): The command wasn't found, is the "gettext" preprocessor installed?