Remove typing-extension dependency on python 3.8 (#1342)

* Remove typing-extension dependency on python 3.8

* retrigger CI

* retrigger CI bis

changes/1342-prettywood.md

@@ -0,0 +1 @@
+Remove `typing_extensions` dependency for python 3.8

requirements.txt

@@ -6,5 +6,5 @@
 devtools==0.5.1
 email-validator==1.0.5
 dataclasses==0.6; python_version < '3.7'
-typing-extensions==3.7.4.1
+typing-extensions==3.7.4.1; python_version < '3.8'
 python-dotenv==0.12.0

tests/test_schema.py

@@ -61,11 +61,6 @@ try:
 except ImportError:
     email_validator = None
 
-try:
-    import typing_extensions
-except ImportError:
-    typing_extensions = None
-
 
 def test_key():
     class ApplePie(BaseModel):
@@ -1459,7 +1454,7 @@ def test_new_type_schema():
     }
 
 
-@pytest.mark.skipif(not typing_extensions, reason='typing_extensions not installed')
+@pytest.mark.skipif(not Literal, reason='typing_extensions not installed and python version < 3.8')
 def test_literal_schema():
     class Model(BaseModel):
         a: Literal[1]