travis-ci started to fail installing `ncdf4` package

[dschlaep]

* installing *source* package ‘ncdf4’ ...
** package ‘ncdf4’ successfully unpacked and MD5 sums checked
configure.ac: starting
checking for nc-config... no
-----------------------------------------------------------------------------------
Error, nc-config not found or not executable.  This is a script that comes with the
netcdf library, version 4.1-beta2 or later, and must be present for configuration
to succeed.

If you installed the netcdf library (and nc-config) in a standard location, nc-config
should be found automatically.  Otherwise, you can specify the full path and name of
the nc-config script by passing the --with-nc-config=/full/path/nc-config argument
flag to the configure script.  For example:

./configure --with-nc-config=/sw/dist/netcdf4/bin/nc-config

Special note for R users:
-------------------------
To pass the configure flag to R, use something like this:

R CMD INSTALL --configure-args="--with-nc-config=/home/joe/bin/nc-config" ncdf4

where you should replace /home/joe/bin etc. with the location where you have
installed the nc-config script that came with the netcdf 4 distribution.
-----------------------------------------------------------------------------------
ERROR: configuration failed for package ‘ncdf4’
* removing ‘/home/travis/R/Library/ncdf4’
Error in i.p(...) : 
  (converted from warning) installation of package ‘ncdf4’ had non-zero exit status
Calls: <Anonymous> ... with_rprofile_user -> with_envvar -> force -> force -> i.p
Execution halted