[FIX] base: prevent module operations while cron is running

closes odoo/odoo#32234

Signed-off-by: Raphael Collet (rco) <rco@openerp.com>

odoo/addons/base/module/module.py

@@ -16,6 +16,7 @@ from docutils.core import publish_string
 from docutils.transforms import Transform, writer_aux
 from docutils.writers.html4css1 import Writer
 import lxml.html
+import psycopg2
 
 try:
     from cStringIO import StringIO
@@ -479,6 +480,14 @@ class Module(models.Model):
 
     @api.multi
     def _button_immediate_function(self, function):
+        try:
+            # This is done because the installation/uninstallation/upgrade can modify a currently
+            # running cron job and prevent it from finishing, and since the ir_cron table is locked
+            # during execution, the lock won't be released until timeout.
+            self._cr.execute("SELECT * FROM ir_cron FOR UPDATE NOWAIT")
+        except psycopg2.OperationalError:
+            raise UserError(_("The server is busy right now, module operations are not possible at"
+                              " this time, please try again later."))
         function(self)
 
         self._cr.commit()