Swagger generator nested ref issue

Error.java

/*
 * Sample API
 * API description in Markdown.
 *
 * OpenAPI spec version: 1.0.0
 * 
 *
 * NOTE: This class is auto generated by the swagger code generator program.
 * https://github.com/swagger-api/swagger-codegen.git
 * Do not edit the class manually.
 */

package io.swagger.client.model;

import java.util.Objects;
import java.util.Arrays;
import com.google.gson.TypeAdapter;
import com.google.gson.annotations.JsonAdapter;
import com.google.gson.annotations.SerializedName;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
// ----------------------------------------------------------------------
// There is no such class in models although DisplayMessage is genereated
// ----------------------------------------------------------------------
import io.swagger.client.model.RefSchemasYamlDisplayMessage;
import io.swagger.v3.oas.annotations.media.Schema;
import java.io.IOException;
/**
 * Error response
 */
@Schema(description = "Error response")
@javax.annotation.Generated(value = "io.swagger.codegen.v3.generators.java.JavaClientCodegen", date = "2019-11-18T15:44:07.799+03:00[Europe/Moscow]")
public class Error {
  /**
   * Error code
   */
  @JsonAdapter(CodeEnum.Adapter.class)
  public enum CodeEnum {
    GENERAL_400("GENERAL_400"),
    ENTITY_404("ENTITY_404"),
    SERVER_500("SERVER_500");

    private String value;

    CodeEnum(String value) {
      this.value = value;
    }
    public String getValue() {
      return value;
    }

    @Override
    public String toString() {
      return String.valueOf(value);
    }
    public static CodeEnum fromValue(String text) {
      for (CodeEnum b : CodeEnum.values()) {
        if (String.valueOf(b.value).equals(text)) {
          return b;
        }
      }
      return null;
    }
    public static class Adapter extends TypeAdapter<CodeEnum> {
      @Override
      public void write(final JsonWriter jsonWriter, final CodeEnum enumeration) throws IOException {
        jsonWriter.value(enumeration.getValue());
      }

      @Override
      public CodeEnum read(final JsonReader jsonReader) throws IOException {
        String value = jsonReader.nextString();
        return CodeEnum.fromValue(String.valueOf(value));
      }
    }
  }  @SerializedName("code")
  private CodeEnum code = null;

  @SerializedName("message")
  private String message = null;

  // ----------------------------------------------------------------------
  // Should be DisplayMessage here
  // ----------------------------------------------------------------------
  @SerializedName("displayMessage")
  private RefSchemasYamlDisplayMessage displayMessage = null;

  public Error code(CodeEnum code) {
    this.code = code;
    return this;
  }

   /**
   * Error code
   * @return code
  **/
  @Schema(description = "Error code")
  public CodeEnum getCode() {
    return code;
  }

  public void setCode(CodeEnum code) {
    this.code = code;
  }

  public Error message(String message) {
    this.message = message;
    return this;
  }

   /**
   * Basic error message
   * @return message
  **/
  @Schema(description = "Basic error message")
  public String getMessage() {
    return message;
  }

  public void setMessage(String message) {
    this.message = message;
  }

  public Error displayMessage(RefSchemasYamlDisplayMessage displayMessage) {
    this.displayMessage = displayMessage;
    return this;
  }

   /**
   * Get displayMessage
   * @return displayMessage
  **/
  @Schema(description = "")
  public RefSchemasYamlDisplayMessage getDisplayMessage() {
    return displayMessage;
  }

  public void setDisplayMessage(RefSchemasYamlDisplayMessage displayMessage) {
    this.displayMessage = displayMessage;
  }


  @Override
  public boolean equals(java.lang.Object o) {
    if (this == o) {
      return true;
    }
    if (o == null || getClass() != o.getClass()) {
      return false;
    }
    Error error = (Error) o;
    return Objects.equals(this.code, error.code) &&
        Objects.equals(this.message, error.message) &&
        Objects.equals(this.displayMessage, error.displayMessage);
  }

  @Override
  public int hashCode() {
    return Objects.hash(code, message, displayMessage);
  }


  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("class Error {\n");
    
    sb.append("    code: ").append(toIndentedString(code)).append("\n");
    sb.append("    message: ").append(toIndentedString(message)).append("\n");
    sb.append("    displayMessage: ").append(toIndentedString(displayMessage)).append("\n");
    sb.append("}");
    return sb.toString();
  }

  /**
   * Convert the given object to string with each line indented by 4 spaces
   * (except the first line).
   */
  private String toIndentedString(java.lang.Object o) {
    if (o == null) {
      return "null";
    }
    return o.toString().replace("\n", "\n    ");
  }

}

ref.yaml

openapi: 3.0.1
info:
  title: Sample API
  description: API description in Markdown.
  version: 1.0.0
servers:
  - url: 'https://api.example.com'
paths:
  /users:
    get:
      summary: Returns a list of users.
      description: Optional extended description in Markdown.
      responses:
        '500':
          $ref: '#/components/responses/Error500'

components:
  schemas:
    DisplayMessage:
      $ref: 'ref_schemas.yaml#/DisplayMessage'
    Error:
      $ref: 'ref_errors.yaml#/Error'
  responses:
    Error500:
      $ref: 'ref_responses.yaml#/Error500'

ref_errors.yaml

# -----------
# Errors
# -----------
Error:
  description: Error response
  type: object
  properties:
    code:
      description: Error code
      type: string
      enum:
        - GENERAL_400
        - ENTITY_404
        - SERVER_500
    message:
      description: Basic error message
      type: string
    displayMessage:
      $ref: './ref_schemas.yaml#/DisplayMessage'

ref_responces.yaml

Error500:
  description: An unexpected error occured.
  content:
    application/vnd.com.navalchess+json:
      schema:
        $ref: './ref_errors.yaml#/Error'

ref_schemas.yaml

DisplayMessage:
  description: Message to display to client
  type: object
  properties:
    header:
      description: Message header
      type: string
    text:
      description: Message text
      type: string