When I create a compute field in odoo i Got below error,

Error:
Odoo Server Error

Traceback (most recent call last):
File "/opt/odoo/odoo/tools/safe_eval\\.py",\\ line\\ 354,\\ in\\ safe_eval
\\ \\ \\ \\ return\\ unsafe_eval\\(c,\\ globals_dict,\\ locals_dict\\)
\\ \\ File\\ "",\\ line\\ 3,\\ in\\
NameError:\\ name\\ 'Warning'\\ is\\ not\\ defined

During\\ handling\\ of\\ the\\ above\\ exception,\\ another\\ exception\\ occurred:

Traceback\\ \\(most\\ recent\\ call\\ last\\):
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 624,\\ in\\ _handle_exception
\\ \\ \\ \\ return\\ super\\(JsonRequest,\\ self\\)\\._handle_exception\\(exception\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 310,\\ in\\ _handle_exception
\\ \\ \\ \\ raise\\ pycompat\\.reraise\\(type\\(exception\\),\\ exception,\\ sys\\.exc_info\\(\\)\\[2\\]\\)
\\ \\ File\\ "/opt/odoo/odoo/tools/pycompat\\.py",\\ line\\ 14,\\ in\\ reraise
\\ \\ \\ \\ raise\\ value
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 669,\\ in\\ dispatch
\\ \\ \\ \\ result\\ =\\ self\\._call_function\\(\\*\\*self\\.params\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 350,\\ in\\ _call_function
\\ \\ \\ \\ return\\ checked_call\\(self\\.db,\\ \\*args,\\ \\*\\*kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/service/model\\.py",\\ line\\ 94,\\ in\\ wrapper
\\ \\ \\ \\ return\\ f\\(dbname,\\ \\*args,\\ \\*\\*kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 339,\\ in\\ checked_call
\\ \\ \\ \\ result\\ =\\ self\\.endpoint\\(\\*a,\\ \\*\\*kw\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 915,\\ in\\ __call__
\\ \\ \\ \\ return\\ self\\.method\\(\\*args,\\ \\*\\*kw\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 515,\\ in\\ response_wrap
\\ \\ \\ \\ response\\ =\\ f\\(\\*args,\\ \\*\\*kw\\)
\\ \\ File\\ "/mnt/extra\\-addons/ks_list_view_manager/controllers/lvm_controller\\.py",\\ line\\ 16,\\ in\\ call_kw
\\ \\ \\ \\ call_kw_result\\ =\\ super\\(LvmController,\\ self\\)\\.call_kw\\(model,\\ method,\\ args,\\ kwargs,\\ path\\)
\\ \\ File\\ "/opt/odoo/odoo/http\\.py",\\ line\\ 515,\\ in\\ response_wrap
\\ \\ \\ \\ response\\ =\\ f\\(\\*args,\\ \\*\\*kw\\)
\\ \\ File\\ "/opt/odoo/odoo/addons/web/controllers/main\\.py",\\ line\\ 1339,\\ in\\ call_kw
\\ \\ \\ \\ return\\ self\\._call_kw\\(model,\\ method,\\ args,\\ kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/addons/web/controllers/main\\.py",\\ line\\ 1331,\\ in\\ _call_kw
\\ \\ \\ \\ return\\ call_kw\\(request\\.env\\[model\\],\\ method,\\ args,\\ kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/api\\.py",\\ line\\ 387,\\ in\\ call_kw
\\ \\ \\ \\ result\\ =\\ _call_kw_multi\\(method,\\ model,\\ args,\\ kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/api\\.py",\\ line\\ 374,\\ in\\ _call_kw_multi
\\ \\ \\ \\ result\\ =\\ method\\(recs,\\ \\*args,\\ \\*\\*kwargs\\)
\\ \\ File\\ "/opt/odoo/odoo/models\\.py",\\ line\\ 6255,\\ in\\ onchange
\\ \\ \\ \\ for\\ name\\ in\\ nametree
\\ \\ File\\ "/opt/odoo/odoo/models\\.py",\\ line\\ 6256,\\ in\\
\\ \\ \\ \\ if\\ name\\ not\\ in\\ done\\ and\\ snapshot0\\.has_changed\\(name\\)
\\ \\ File\\ "/opt/odoo/odoo/models\\.py",\\ line\\ 6101,\\ in\\ has_changed
\\ \\ \\ \\ return\\ self\\[name\\]\\ !=\\ record\\[name\\]
\\ \\ File\\ "/opt/odoo/odoo/models\\.py",\\ line\\ 5731,\\ in\\ __getitem__
\\ \\ \\ \\ return\\ self\\._fields\\[key\\]\\.__get__\\(self,\\ type\\(self\\)\\)
\\ \\ File\\ "/opt/odoo/odoo/fields\\.py",\\ line\\ 1032,\\ in\\ __get__
\\ \\ \\ \\ self\\.compute_value\\(recs\\)
\\ \\ File\\ "/opt/odoo/odoo/fields\\.py",\\ line\\ 1146,\\ in\\ compute_value
\\ \\ \\ \\ records\\._compute_field_value\\(self\\)
\\ \\ File\\ "/opt/odoo/odoo/models\\.py",\\ line\\ 4005,\\ in\\ _compute_field_value
\\ \\ \\ \\ field\\.compute\\(self\\)
\\ \\ File\\ "/opt/odoo/odoo/addons/base/models/ir_model\\.py",\\ line\\ 33,\\ in\\
\\ \\ \\ \\ func\\ =\\ lambda\\ self:\\ safe_eval\\(text,\\ SAFE_EVAL_BASE,\\ \\{'self':\\ self\\},\\ mode="exec"\\)
\\ \\ File\\ "/opt/odoo/odoo/tools/safe_eval\\.py",\\ line\\ 377,\\ in\\ safe_eval
\\ \\ \\ \\ pycompat\\.reraise\\(ValueError,\\ ValueError\\('%s:\\ "%s"\\ while\\ evaluating\n%r'\\ %\\ \\(ustr\\(type\\(e\\)\\),\\ ustr\\(e\\),\\ expr\\)\\),\\ exc_info\\[2\\]\\)
\\ \\ File\\ "/opt/odoo/odoo/tools/pycompat\\.py",\\ line\\ 13,\\ in\\ reraise
\\ \\ \\ \\ raise\\ value\\.with_traceback\\(tb\\)
\\ \\ File\\ "/opt/odoo/odoo/tools/safe_eval\\.py",\\ line\\ 354,\\ in\\ safe_eval
\\ \\ \\ \\ return\\ unsafe_eval\\(c,\\ globals_dict,\\ locals_dict\\)
\\ \\ File\\ "",\\ line\\ 3,\\ in\\
ValueError:\\ :\\ "name\\ 'Warning'\\ is\\ not\\ defined"\\ while\\ evaluating
"for\\ rec\\ in\\ self:\n\\ \\ if\\ rec\\.date_time\\ >\\ datetime.datetime.now():\n raise Warning('blah blah blah')"

If I use automated action it work perfectly