patch 8.2.3967: error messages are spread out

Problem:    Error messages are spread out.
Solution:   Move more errors to errors.h.
diff --git a/src/channel.c b/src/channel.c
index 5133440..ec91739 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -161,7 +161,7 @@
 	file = fopen((char *)fname, *opt == 'w' ? "w" : "a");
 	if (file == NULL)
 	{
-	    semsg(_(e_notopen), fname);
+	    semsg(_(e_cant_open_file_str), fname);
 	    return;
 	}
 	vim_free(log_name);