Duplicate message by configure

[Gerald Pfeifer]

Disclaimer: I am aware that the system I tested this on is lacking a
required library, this is not what I'm trying to describe.

When running configure, I get the following message twice:

   checking for xmlParseMemory in -lxml2... yes
   checking for xmlReadMemory in -lxml2... yes
   Package libxslt was not found in the pkg-config search path.
   Perhaps you should add the directory containing `libxslt.pc'
   to the PKG_CONFIG_PATH environment variable
   No package 'libxslt' found
-> Package libxslt was not found in the pkg-config search path.
-> Perhaps you should add the directory containing `libxslt.pc'
-> to the PKG_CONFIG_PATH environment variable
-> No package 'libxslt' found
   checking for libxslt/pattern.h... no
   checking for libxslt/transform.h... no

Where does this come from?  Can we fix this somehow?

Gerald