Use nowide from Boost. From Fedora.

Index: util/tests/environment.cc
--- util/tests/environment.cc.orig
+++ util/tests/environment.cc
@@ -1,6 +1,6 @@
 #include <catch.hpp>
 #include <leatherman/util/environment.hpp>
-#include <boost/nowide/cenv.hpp>
+#include <boost/nowide/cstdlib.hpp>
 
 using namespace std;
 using namespace leatherman::util;
