[http-client-python] Enum name cause compile error

[tadelesh]

For this following spec, python emitter will generate the enum with - which could not pass compile.

union EAPMethod {
  string,

  /** PEAP authentication. */
  PEAP: "PEAP",

  /** EAP-TLS authentication. */
  `EAP-TLS`: "EAP-TLS",

  /** EAP-TTLS authentication. */
  `EAP-TTLS`: "EAP-TTLS",

  /** EAP-FAST authentication. */
  `EAP-FAST`: "EAP-FAST",
}