Today I found this error when I tried to update to wordpress version to 4.3.1. Remember, my wordpress was hosted in IIS with Windows Server 2008 R2 Standard. In the past whenever I tried to update the wordpress it worked like charm.
It was very frustrating for me to suddenly receive the error
Download failed. There are no HTTP transports available which can complete the requested request.On googling I found to uncomment the following extensions from php.ini