Swagger / OpenAPI spec featuring file upload rejected by Google Endpoints

[Raffael]

Hello!

My goal is to set up a simple API for uploading a file via Google Endpoints.

This is my simplified OpenAPI specification which is valid according to Swagger validation:

swagger: "2.0"
info:
  title: "JSON Ingester"
  description: "Receive JSON files, transform and load them."
  version: "1.0.0"


host: "project-id.appspot.com"
schemes:
  - "https"


paths:
  /uploadFile:
    post:
      operationId: uploadFile
      consumes:
        - multipart/form-data
      parameters:
        -
          in: formData
          name: upfile
          type: file
          description: file
      responses:
        200:
          description: "File uploaded."
        400:
          description: "Error during file upload."

Here comes the dummy Flask controller for the upload (though, I guess it is irrelevant to the problem):

@app.route('/uploadFile', methods=['POST'])
def uploadFile():
    return

I always end up with this obscure error message:

user@cloudshell:~/google-cloud-json-ingester (project-id)$ gcloud endpoints services deploy ./openapi.yaml
ERROR: (gcloud.endpoints.services.deploy) INVALID_ARGUMENT: Cannot convert to service config.
'location: "openapi.yaml: Operation \'post\' in path \'/uploadFile\'"
message: "Operation does not require an API key; callers may invoke the method without specifying an associated API-consuming project. To enable API key all the SecurityRequirement Objects (https://gi
thub.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#security-requirement-object) inside security definition must reference at least one SecurityDefinition of type : \'apiKey\'."
 location: "unknown location"
kind: ERROR
message: "http: repeated message field \'google.protobuf.Struct.fields\' referred to by message \'UploadFileRequest\' cannot be mapped as an HTTP parameter."
 location: "unknown location"
kind: ERROR
message: "http: cyclic message field \'google.protobuf.Struct.FieldsEntry.value\' referred to by message \'UploadFileRequest\' in method \'method 1.project_id_appspot_com.UploadFile\' cannot
 be mapped as an HTTP parameter."
 location: "unknown location"
kind: ERROR
message: "http: cyclic message field \'google.protobuf.ListValue.values\' referred to by message \'UploadFileRequest\' in method \'method 1.project_id_appspot_com.UploadFile\' cannot be mapp
ed as an HTTP parameter."
'

I've run out of ideas as to what might be the cause.

Any suggestions?