Getting "UnknownError: Forbidden: DynamoDB" on migrate

running ```sls dynamodb start```
with a configuration as shown below(migrate: true and a configured Table resource)
shows error "UnknownError: Forbidden: DynamoDB - Error -"
and does not migrate the table.
With migrate: false there is no error

**Expected Behaviour**

should create the configured tables if migrate: true is configured

**Steps to reproduce it**
This is the relevant part of the serverless.yaml:

```
provider:
name: aws
runtime: nodejs12.x
region: eu-central-1
stage: 'offline'
custom:
serverless-offline:
port: 2110
stage: offline
dynamodb:
start:
port: 8000
inMemory: true
migrate: true
stages:
- offline
plugins:
- serverless-dynamodb-local
- serverless-offline
resources:
Resources:
DevicesTable:
Type: 'AWS::DynamoDB::Table'
DeletionPolicy: Retain
Properties:
AttributeDefinitions:
- AttributeName: userId
AttributeType: S
- AttributeName: created
AttributeType: N
KeySchema:
- AttributeName: userId
KeyType: HASH
- AttributeName: created
KeyType: RANGE
ProvisionedThroughput:
ReadCapacityUnits: 1
WriteCapacityUnits: 1
TableName: 'MyTable'
```

**LogCat for the issue**

```
Serverless: Running "serverless" installed locally (in service node_modules)
Dynamodb Local Started, Visit: http://localhost:8000/shell

UnknownError: Forbidden: DynamoDB - Error -

Unknown Error ------------------------------------------

UnknownError: Forbidden
at Request.extractError (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\protocol\json.js:52:27)
at Request.callListeners (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\sequential_executor.js:106:20)
at Request.emit (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\sequential_executor.js:78:10)
at Request.emit (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\request.js:690:14)
at Request.transition (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\request.js:22:10)
at AcceptorStateMachine.runTo (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\state_machine.js:14:12)
at Request. (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\request.js:38:9)
at Request. (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\request.js:692:12)
at Request.callListeners (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\sequential_executor.js:116:18)
at callNextListener (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\sequential_executor.js:96:12)
at IncomingMessage.onEnd (C:\Users\me\projects\assethub\device-backend\node_modules\aws-sdk\lib\event_listeners.js:313:13)
at IncomingMessage.emit (events.js:215:7)
at IncomingMessage.EventEmitter.emit (domain.js:476:20)
at endReadableNT (_stream_readable.js:1183:12)
at processTicksAndRejections (internal/process/task_queues.js:80:21)

```

I also logged the constructor arguments for the last request before the failure (service, operation and params)
```
Service: Service {
config: Config {
credentials: Credentials {
expired: false,
expireTime: null,
refreshCallbacks: [],
accessKeyId: 'MOCK_ACCESS_KEY_ID',
sessionToken: undefined
},
credentialProvider: CredentialProviderChain {
providers: [Array],
resolveCallbacks: []
},
region: 'localhost',
logger: null,
apiVersions: {},
apiVersion: null,
endpoint: 'http://localhost:8000',
httpOptions: { timeout: 120000, agent: [HttpsProxyAgent] },
maxRetries: undefined,
maxRedirects: 10,
paramValidation: true,
sslEnabled: true,
s3ForcePathStyle: false,
s3BucketEndpoint: false,
s3DisableBodySigning: true,
s3UsEast1RegionalEndpoint: 'legacy',
s3UseArnRegion: undefined,
computeChecksums: true,
convertResponseTypes: true,
correctClockSkew: false,
customUserAgent: null,
dynamoDbCrc32: true,
systemClockOffset: 0,
signatureVersion: null,
signatureCache: true,
retryDelayOptions: {},
useAccelerateEndpoint: false,
clientSideMonitoring: false,
endpointDiscoveryEnabled: undefined,
endpointCacheSize: 1000,
hostPrefixEnabled: true,
stsRegionalEndpoints: 'legacy',
accessKeyId: 'MOCK_ACCESS_KEY_ID',
secretAccessKey: 'MOCK_SECRET_ACCESS_KEY',
convertEmptyValues: false
},
endpoint: Endpoint {
protocol: 'http:',
host: 'localhost:8000',
port: 8000,
hostname: 'localhost',
pathname: '/',
path: '/',
href: 'http://localhost:8000/'
},
_events: {
apiCallAttempt: [ [Function: EVENTS_BUBBLE] ],
apiCall: [ [Function: CALL_EVENTS_BUBBLE] ]
},
MONITOR_EVENTS_BUBBLE: [Function: EVENTS_BUBBLE],
CALL_EVENTS_BUBBLE: [Function: CALL_EVENTS_BUBBLE],
_clientId: 1
}
operation: createTable
params: {
AttributeDefinitions: [
{ AttributeName: 'userId', AttributeType: 'S' },
{ AttributeName: 'created', AttributeType: 'N' }
],
KeySchema: [
{ AttributeName: 'userId', KeyType: 'HASH' },
{ AttributeName: 'created', KeyType: 'RANGE' }
],
ProvisionedThroughput: { ReadCapacityUnits: 1, WriteCapacityUnits: 1 },
TableName: 'MyTable'
}

```
I'm on Windows 10 and used gitbash.
```
Your Environment Information ---------------------------
Operating System: win32
Node Version: 12.13.0
Framework Version: 2.19.0
Plugin Version: 4.4.2
SDK Version: 2.3.2
Components Version: 3.4.7
```
The default credentials in my .aws/credentials file are valid:

```aws dynamodb list-tables --no-verify-ssl```

shows the table in my AWS account

I use the same credentials to deploy the whole application with serverless (which creates also the dynamodb tables)

If I use the params from the debug log above in localhost:8000/shell to create the table it works with no error and the table is created.

I am behind a proxy but as mentioned aws cli works fine (but needs --no-verify-ssl )

If any more information is needed I'm willing to provide it!
Any hint how to debug the error is welcome too!

Reproduce the failure with `sls dynamodb start` and the `serverless.yaml` configuration shown, then trace the plugin's migrate entry point through the logged `createTable` request. Compare the local request with the working DynamoDB Local shell request and inspect the surrounding AWS SDK configuration. Done means `migrate: true` creates the configured table without the Forbidden error.

Written by the indexing model from the issue text.