[IMP] Fixed with context bug.

project_timesheet_matrix/models/project_project.py

@@ -4,9 +4,8 @@ from odoo import models, fields, api
 class ProjectProject(models.Model):
     _inherit = "project.project"
 
-    @api.model
+    @api.multi
     def open_timesheets_matrix(self):
-        import pdb; pdb.set_trace()
         wiz = self.env['project.timesheet.matrix.wiz'].create({})
         return {
             'name': 'Edit timesheets',