fix minus sign in enum naming in python-nextgen (#15291)

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/PythonNextgenClientCodegen.java

@@ -1518,7 +1518,7 @@ public class PythonNextgenClientCodegen extends AbstractPythonCodegen implements
 
     public String toEnumVariableName(String name, String datatype) {
         if ("int".equals(datatype)) {
-            return "NUMBER_" + name;
+            return "NUMBER_" + name.replace("-", "MINUS_");
         }
 
         // remove quote e.g. 'abc' => abc

modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml

@@ -1864,6 +1864,7 @@ components:
     OuterEnumIntegerDefaultValue:
       type: integer
       enum:
+      - -1
       - 0
       - 1
       - 2

samples/openapi3/client/petstore/python-nextgen-aiohttp/petstore_api/models/outer_enum_integer_default_value.py

@@ -29,6 +29,7 @@ class OuterEnumIntegerDefaultValue(int, Enum):
     """
     allowed enum values
     """
+    NUMBER_MINUS_1 = -1
     NUMBER_0 = 0
     NUMBER_1 = 1
     NUMBER_2 = 2

samples/openapi3/client/petstore/python-nextgen/petstore_api/models/outer_enum_integer_default_value.py

@@ -29,6 +29,7 @@ class OuterEnumIntegerDefaultValue(int, Enum):
     """
     allowed enum values
     """
+    NUMBER_MINUS_1 = -1
     NUMBER_0 = 0
     NUMBER_1 = 1
     NUMBER_2 = 2