Comment # 3 on bug 1202003 from Eric Schirra

Don't know what I can do.
There is also needed for build.
And under documentation:Tools it was first build. You can see new version
6.2.1.
So I make a request for factory.
And after some hours it was no more build.
It is require for build and build starts. 
Then in build time it rise up an error not and say mechanize was not installed.
For me it is not an error in calibre build.
It is an error in mechanize build.