Fixed error handling in less-pretty-cat plugin

When pygmentize is not installed, the functions less/cat are not
defined, the native commands will be used instead. Also removed the
error message that was shown when the command was not found.

Using `command -v` instead of `which` to check for the existence of the
executable - this works better as it does not print an error message if
the executable is not found.

plugins/available/less-pretty-cat.plugin.bash

@@ -1,19 +1,14 @@
 cite about-plugin
 about-plugin 'pygmentize instead of cat to terminal if possible'
 
-if [ -z $(which pygmentize) ]
+if $(command -v pygmentize &> /dev/null) ; then
-then
+  # get the full paths to binaries
-    echo "Pygments is required to use this plugin"
+  CAT_BIN=$(which cat)
-    echo "Install it by doing 'pip install Pygments' as the superuser"
+  LESS_BIN=$(which less)
-fi
 
-# get the full paths to binaries
+  # pigmentize cat and less outputs
-CAT_BIN=$(which cat)
+  function cat()
-LESS_BIN=$(which less)
+  {
-
-# pigmentize cat and less outputs
-cat()
-{
       about 'runs either pygmentize or cat on each file passed in'
       param '*: files to concatenate (as normally passed to cat)'
       example 'cat mysite/manage.py dir/text-file.txt'
@@ -21,12 +16,13 @@ cat()
       do
           pygmentize "$var" 2>/dev/null || "$CAT_BIN" "$var";
       done
-}
+  }
 
-less()
+  function less()
-{
+  {
       about 'it pigments the file passed in and passes it to less for pagination'
       param '$1: the file to paginate with less'
       example 'less mysite/manage.py'
       pygmentize "$*" | "$LESS_BIN" -R
-}
+  }
+fi