Preserve encoding in error messages for invalid user/group name

process.c

@@ -5585,7 +5585,7 @@ obj2uid(VALUE id
 #ifndef USE_GETPWNAM_R
 	    endpwent();
 #endif
-	    rb_raise(rb_eArgError, "can't find user for %s", usrname);
+            rb_raise(rb_eArgError, "can't find user for %"PRIsVALUE, id);
 	}
 	uid = pwptr->pw_uid;
 #ifndef USE_GETPWNAM_R
@@ -5664,7 +5664,7 @@ obj2gid(VALUE id
 #if !defined(USE_GETGRNAM_R) && defined(HAVE_ENDGRENT)
 	    endgrent();
 #endif
-	    rb_raise(rb_eArgError, "can't find group for %s", grpname);
+            rb_raise(rb_eArgError, "can't find group for %"PRIsVALUE, id);
 	}
 	gid = grptr->gr_gid;
 #if !defined(USE_GETGRNAM_R) && defined(HAVE_ENDGRENT)

test/ruby/test_process.rb

@@ -1610,6 +1610,9 @@ class TestProcess < Test::Unit::TestCase
       if u = Etc.getpwuid(Process.uid)
         assert_equal(Process.uid, Process::UID.from_name(u.name), u.name)
       end
+      assert_raise_with_message(ArgumentError, /\u{4e0d 5b58 5728}/) {
+        Process::UID.from_name("\u{4e0d 5b58 5728}")
+      }
     end
   end
 
@@ -1618,6 +1621,9 @@ class TestProcess < Test::Unit::TestCase
       if g = Etc.getgrgid(Process.gid)
         assert_equal(Process.gid, Process::GID.from_name(g.name), g.name)
       end
+      assert_raise_with_message(ArgumentError, /\u{4e0d 5b58 5728}/) {
+        Process::GID.from_name("\u{4e0d 5b58 5728}")
+      }
     end
   end