*: fix unstable assert for location (#53376)

close #53375

pkg/expression/context/context.go

@@ -146,10 +146,11 @@ func (ctx *NullRejectCheckExprContext) IsInNullRejectCheck() bool {
 // AssertLocationWithSessionVars asserts the location in the context and session variables are the same.
 // It is only used for testing.
 func AssertLocationWithSessionVars(ctxLoc *time.Location, vars *variable.SessionVars) {
-	varsLoc := vars.Location()
-	stmtLoc := vars.StmtCtx.TimeZone()
-	intest.Assert(ctxLoc == varsLoc && ctxLoc == stmtLoc,
+	ctxLocStr := ctxLoc.String()
+	varsLocStr := vars.Location().String()
+	stmtLocStr := vars.StmtCtx.TimeZone().String()
+	intest.Assert(ctxLocStr == varsLocStr && ctxLocStr == stmtLocStr,
 		"location mismatch, ctxLoc: %s, varsLoc: %s, stmtLoc: %s",
-		ctxLoc.String(), varsLoc.String(), stmtLoc.String(),
+		ctxLoc.String(), ctxLocStr, stmtLocStr,
 	)
 }