backup: show errors at top of email notification

backup.py

@@ -470,17 +470,24 @@ def main(argv: typing.List[str]):
         if email and not args.dry_run:
             backup.log('I', f"sending error notification to {email}")
 
-            # Show all of our log output.  Use a ":" prefix for
-            # warnings, errors, and notices so that they get
-            # highlighted by the mail reader.
-            body = [ "Logs:" ]
-            for (letter, msg) in backup.logs:
-                if letter in "EWN":
-                    prefix = ":"
-                else:
-                    prefix = " "
-                body.append(f"{prefix}{letter}: {msg}")
-            body_text = "\n".join(body).encode()
+            def write_logs(title, only_include=None):
+                body = [ title ]
+                for (letter, msg) in backup.logs:
+                    if only_include and letter not in only_include:
+                        continue
+                    # Use a ":" prefix for warnings/errors/notices so that
+                    # the mail reader highlights them.
+                    if letter in "EWN":
+                        prefix = ":"
+                    else:
+                        prefix = " "
+                    body.append(f"{prefix}{letter}: {msg}")
+                return "\n".join(body).encode()
+
+
+            body_text = write_logs("Logged errors and warnings:", "EWN")
+            body_text += "\n"
+            body_text += write_logs("All logs:")
 
             # Subject summary
             if errmsg and warnmsg: