Flexget: API "PUT" method for variables endpoint fails to update variables.yml

Expected behaviour: The variables.yml file to be updated to reflect the json payload sent via curl.

Actual behaviour: No updates are made.

Steps to reproduce:

• Step 1: Create variables.yml file with only the following single line:

a:b

• Step 2: From terminal, execute: curl -X PUT --header 'Content-Type: application/json' --header 'Accept: application/json' --header 'Authorization: Token TOKEN_REDACTED' -d '{"a":"c"}' 'http://localhost:5050/api/variables/'

• Step 3: Observe output as: a:b

Config:

variables: /path/to/flexget/variables.yml
web_server: yes
templates:
  dl:
    deluge: yes
....
...
...

Variables:

a: b

Log:

No information was added to the log after the API call.

Additional information:

• FlexGet version: 2.21.25
• Python version: 3.7.3
• Installation method: pip3
• Using daemon (yes/no): yes
• OS and version: Kubuntu 19.04
• Link to crash log: null