Merge branch 'master' into more-fmtlib-and-string

# Conflicts:
#	src/write_restart.cpp

src/balance.cpp

@@ -475,7 +475,9 @@ void Balance::options(int iarg, int narg, char **arg)
 
   if (outflag && comm->me == 0) {
     fp = fopen(arg[outarg],"w");
-    if (fp == NULL) error->one(FLERR,"Cannot open (fix) balance output file");
+    if (fp == NULL)
+      error->one(FLERR,fmt::format("Cannot open (fix) balance output file {}: {}",
+                                   arg[outarg], utils::getsyserror()));
   }
 }