feat: ignore tar: file changed as we read it during backups

This seems to occur when new files are being created as we're archiving
the files on a site. Doesn't make sense to fail the entire backup
because of that.

Signed-off-by: Akhil Narang <me@akhilnarang.dev>

frappe/exceptions.py

@@ -300,3 +300,10 @@ class InvalidKeyError(ValidationError):
 	http_status_code = 401
 	title = "Invalid Key"
 	message = "The document key is invalid"
+
+
+class CommandFailedError(Exception):
+	def __init__(self, message: str, out: str, err: str):
+		super().__init__(message)
+		self.out = out
+		self.err = err

frappe/utils/__init__.py

@@ -482,7 +482,7 @@ def execute_in_shell(cmd, verbose=False, low_priority=False, check_exit_code=Fal
 			print(out)
 
 	if failed:
-		raise Exception("Command failed")
+		raise frappe.CommandFailedError("Command failed", out.decode(), err.decode())
 
 	return err, out
 

frappe/utils/backups.py

@@ -352,12 +352,21 @@ class BackupGenerator:
 			else:
 				cmd_string = "tar -cf {0} {1}"
 
-			frappe.utils.execute_in_shell(
-				cmd_string.format(backup_path, files_path),
-				verbose=self.verbose,
-				low_priority=True,
-				check_exit_code=True,
-			)
+			try:
+				frappe.utils.execute_in_shell(
+					cmd_string.format(backup_path, files_path),
+					verbose=self.verbose,
+					low_priority=True,
+					check_exit_code=True,
+				)
+			except frappe.CommandFailedError as e:
+				if e.err and "file changed as we read it" in e.err:
+					click.secho(
+						"Ignoring `tar: file changed as we read it` to prevent backup failure",
+						fg="red",
+					)
+				else:
+					raise e
 
 	def copy_site_config(self):
 		site_config_backup_path = self.backup_path_conf