[IMP] contract: possible error in migration if the column does not exist

contract/migrations/11.0.2.0.0/pre-migration.py

@@ -7,6 +7,11 @@ def migrate(cr, version):
     """Rename column for specific price for keeping backwards compatibility."""
     if not version:
         return
+    cr.execute("""SELECT column_name
+        FROM information_schema.columns
+        WHERE table_name='account_analytic_invoice_line' AND
+        column_name='price_unit'""")
+    if cr.fetchone():
         cr.execute(
             "ALTER TABLE account_analytic_invoice_line "
             "RENAME price_unit TO specific_price"