[Python] Ensure we generate correct string literals in Python unions (#2478)

* Make sure string literals are valid

* Remove raw string marker

* Remove jsonrpc model

* Add commented JsonRPC1.0 model

Author: crisidev

codegen-server-test/python/build.gradle.kts

@@ -54,6 +54,14 @@ val allCodegenTests = "../../codegen-core/common-test-models".let { commonModels
             // TODO(https://github.com/awslabs/smithy-rs/issues/1401) `@uniqueItems` is used.
             extraConfig = """, "codegen": { "ignoreUnsupportedConstraints": true } """,
         ),
+        // TODO(https://github.com/awslabs/smithy-rs/issues/2476)
+        // CodegenTest(
+        //     "aws.protocoltests.json#JsonProtocol",
+        //     "json_rpc11",
+        //     extraConfig = """, "codegen": { "ignoreUnsupportedConstraints": true } """,
+        // ),
+        // TODO(https://github.com/awslabs/smithy-rs/issues/2479)
+        // CodegenTest("aws.protocoltests.json10#JsonRpc10", "json_rpc10"),
     )
 }
 

codegen-server/python/src/main/kotlin/software/amazon/smithy/rust/codegen/server/python/smithy/generators/PythonServerUnionGenerator.kt

@@ -186,7 +186,7 @@ class PythonServerUnionGenerator(
                     match self.0.as_$funcNamePart() {
                         Ok(variant) => Ok($variantType),
                         Err(_) => Err(#{pyo3}::exceptions::PyValueError::new_err(
-                            "${unionSymbol.name} variant is not of type ${memberSymbol.rustType().pythonType().renderAsDocstring()}"
+                            r"${unionSymbol.name} variant is not of type ${memberSymbol.rustType().pythonType().renderAsDocstring()}"
                         )),
                     }
                     """,