Check that networkcache was correctly installed.

src/zc/buildout/networkcache.txt

@@ -29,7 +29,17 @@ So lets activate networkcache in buildout:
    ...   slapos.libnetworkcache
    ...   zc.buildout
    ... ''')
-   >>> ignore = system(buildout)
+   >>> ignored = system(buildout)
+
+Lets check that networkcache is correclty installed:
+   >>> write(sample_buildout, 'buildout.cfg',
+   ... '''
+   ... [buildout]
+   ... parts =
+   ... ''')
+   >>> print system(buildout + ' -v')
+   Networkcache functionality not enabled. In order to activate use networkcache-section.
+   ...
 
 Now let's prepare networkcache server:
    >>> nc_data = tmpdir('nc_data')