add a log hint for mismatched brackets

services/web/public/coffee/ide/human-readable-logs/HumanReadableLogsRules.coffee

@@ -93,6 +93,14 @@ define -> [
 		regexToMatch: /Error: `([^']{2,})' expected, found `([^']{2,})'.*/
 		newMessage: "Error: environment does not match \\begin{$1} ... \\end{$2}"
 		humanReadableHint: """
-			You have used \\begin{...} without a corresponding \\end{...}
+			You have used \\begin{...} without a corresponding \\end{...}.
 		"""
+	,
+		ruleId: "hint_mismatched_brackets"
+		regexToMatch: /Error: `([^a-zA-Z0-9])' expected, found `([^a-zA-Z0-9])'.*/
+		newMessage: "Error: brackets do not match, found '$2' instead of '$1'"
+		humanReadableHint: """
+			You have used an open bracket without a corresponding close bracket.
+		"""
+
 ]