Rubyonrails 在 ruby​​ 中构建公钥时，是什么导致既不是 PUB key 也不是 PRIV key：：nested asn1 错误

当使用OpenSSL::PKey::RSA模块通过传递.pem文件，响应的原因是什么:

OpenSSL::PKey::RSAError: Neither PUB key nor PRIV key:: nested asn1 error
from /Users/Matt/projects/placepop/lib/apn.rb:48:in `initialize'
from /Users/Matt/projects/placepop/lib/apn.rb:48:in `new'
from /Users/Matt/projects/placepop/lib/apn.rb:48:in `open'
from (irb):1

以下是消息来源:

cert = File.join(rails_root, 'config', 'apns', 'sandbox-cert.pem')
APN_CONFIG = { :delivery => { 
                              :host => 'gateway.sandbox.push.apple.com', 
                              :cert => cert,
                              :passphrase => "",
                              :port => 2195 },
               :feedback => {  
                              :host => 'feedback.sandbox.push.apple.com',
                              :port => 2196,
                              :passphrase => "",
                              :cert => cert} }


options = APN_CONFIG[:delivery].merge(options)
cert = File.read(options[:cert])
ctx = OpenSSL::SSL::SSLContext.new
ctx.key = OpenSSL::PKey::RSA.new(cert, options[:passphrase])
ctx.cert = OpenSSL::X509::Certificate.new(cert)

sock = TCPSocket.new(options[:host], options[:port])
ssl = OpenSSL::SSL::SSLSocket.new(sock, ctx)
ssl.sync = true
ssl.connect