Serverless error - The CloudFormation template is invalid - during deployment

Serverless Framework
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1

When deploying lambdas with serverless, the following error occurs:

The CloudFormation template is invalid: Template format error: Output ServerlessDeploymentBucketName is malformed. The Name field of every Export member must be specified and consist only of alphanumeric characters, colons, or hyphens.

I don’t understand what the problem is.

Serverless config file:

service: lambdas-${opt:region}

frameworkVersion: '2'

provider:
  name: aws
  runtime: nodejs12.x
  memorySize: 512
  timeout: 10
  lambdaHashingVersion: 20201221
  region: ${opt:region}
  stackName: lambdas-${opt:region}
  logRetentionInDays: 14
  deploymentBucket:
    name: lambdas-${opt:region}

plugins:
  - serverless-deployment-bucket

functions:
  function1:
    handler: function1/index.handler
    name: function1-${opt:stage}
    description: This function should call specific API on Backend server
    events:
      - schedule: cron(0 0 * * ? *)
    environment:
      ENV: ${opt:stage}
  function2:
    handler: function2/index.handler
    name: function2-${opt:stage}
    description: Function should be triggered by invocation from backend.
    environment:
      ENV: ${opt:stage}