6256: Can't create graph reports


git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21011 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
display error messages correctly

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21014 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
typo in args error reporting

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21017 4ae1f11a-8b86-4847-b8af-ab372f36d1fd