Create a symbolic link to the specified file in the
        directory containing the input files of the task.

def inlink_file(self, filepath):
        """
        Create a symbolic link to the specified file in the
        directory containing the input files of the task.
        """
        if not os.path.exists(filepath):
            logger.debug("Creating symbolic link to not existent file %s" % filepath)

        # Extract the Abinit extension and add the prefix for input files.
        root, abiext = abi_splitext(filepath)

        infile = "in_" + abiext
        infile = self.indir.path_in(infile)

        # Link path to dest if dest link does not exist.
        # else check that it points to the expected file.
        self.history.info("Linking path %s --> %s" % (filepath, infile))

        if not os.path.exists(infile):
            os.symlink(filepath, infile)
        else:
            if os.path.realpath(infile) != filepath:
                raise self.Error("infile %s does not point to filepath %s" % (infile, filepath))