fails:Net::HTTPHeader#fetch when passed key returns the header entry for the passed key
fails:Net::HTTPHeader#fetch when passed key is case-insensitive
fails:Net::HTTPHeader#fetch when passed key returns nil when there is no entry for the passed key
fails:Net::HTTPHeader#fetch when passed key, default returns the header entry for the passed key
fails:Net::HTTPHeader#fetch when passed key, default returns the default value when there is no entry for the passed key
fails:Net::HTTPHeader#fetch when passed key and block returns the header entry for the passed key
fails:Net::HTTPHeader#fetch when passed key and block yieldsand returns the block's return value when there is no entry for the passed key
