Set locale for all "make check" targets.

plugins/python/Makefile.in

@@ -224,6 +224,12 @@ fuzz:
 
 check: $(TEST_PROGS)
 	@if test X"$(cross_compiling)" != X"yes"; then \
+	    if locale -a 2>&1 | grep '^C.UTF-8$$' >/dev/null 2>&1; then \
+		LC_ALL=C.UTF-8; export LC_ALL; \
+	    else \
+		LC_ALL=C; export LC_ALL; \
+	    fi; \
+	    unset LANG || LANG=; \
 	    MALLOC_OPTIONS=S; export MALLOC_OPTIONS; \
 	    MALLOC_CONF="abort:true,junk:true"; export MALLOC_CONF; \
             ./check_python_examples ".libs/python_plugin.so"; \