Don't crash keyword compilation on broken locales

Work around a weakness of older boosts by forcing C locale if
std::locale throws.

The real solution is to not have broken locales, but this should make it
slightly easier to get the JSON keywords compiled.

opm/parser/eclipse/Parser/createDefaultKeywordList.cpp

@@ -16,13 +16,21 @@
   You should have received a copy of the GNU General Public License
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
+
+#if !defined(WIN32)
+    #define _POSIX_C_SOURCE 200112L
+    #include <stdlib.h>
+#endif
+
 #include <iostream>
+#include <locale>
+
+#include <boost/filesystem.hpp>
 
 #include <opm/parser/eclipse/Generator/KeywordGenerator.hpp>
 #include <opm/parser/eclipse/Generator/KeywordLoader.hpp>
 
 
-
 int main(int argc , char ** argv) {
     if (argc == 7) {
         const char * config_root = argv[1];
@@ -34,6 +42,33 @@ int main(int argc , char ** argv) {
         bool verboseLoader = false;
         bool verboseGenerator = true;
 
+        try {
+            /* sometimes the local env's locales are broken on POSIX. Boost <=
+             * 1.56 uses the std::locale("") constructor which respects user
+             * preferred locales, and might crash. If this is the case, and
+             * we're on a non-windows system (assuming POSIX), in case of an
+             * exception, set the environment to "C" and keep going.
+             *
+             * Can be removed once boost < 1.57 is no longer supported
+             */
+            std::locale( "" );
+        } catch( const std::runtime_error& ) {
+            #if !defined(WIN32)
+            setenv( "LC_ALL", "C", 1 );
+            #endif
+            auto loc = boost::filesystem::path::imbue( std::locale::classic() );
+            boost::filesystem::path::imbue( loc );
+            std::cout << "User preferred locale setting is invalid "
+                      << "which breaks Boost <= 1.56 "
+                      << "- forcing to 'C' as workaround for Boost <= 1.56. "
+                      << "This workaround only applies to compile opm-parser, "
+                      << "but your locale settings seem BROKEN, "
+                      << "and opm-parser is likely NOT GOING TO WORK. "
+                      << "If you're on linux you can try setting the LANG "
+                      << "or LC_ALL environment variables to C or POSIX."
+                      << std::endl;
+        }
+
         Opm::KeywordLoader loader(verboseLoader);
         Opm::KeywordGenerator generator(verboseGenerator);
         loader.loadMultipleKeywordDirectories( config_root );