If when attempting to install a plugin via magento connect and you get this error:
Unknown cipher in list: TLSv1 [duplicate]
Then a quick fix is to open this file:
downloader/lib/Mage/HTTP/Client/Curl.php
And to change this line:
$this->curlOption(CURLOPT_SSL_CIPHER_LIST, 'TLSv1');
To this:
$this->curlOption(CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1);