Apache 2.4.9 在启用 SSL 模块并设置 SSL 证书后失败

Apache 在尝试设置 SSL 证书后抛出以下错误：

[ssl:emerg] [pid 30907] AH02572: Failed to configure at least one certificate and key for localhost:443
[ssl:emerg] [pid 30907] SSL Library Error: error:140A80B1:SSL routines:SSL_CTX_check_private_key:no certificate assigned
[ssl:emerg] [pid 30907] AH02312: Fatal error initialising mod_ssl, exiting.

我使用 MAC 操作系统：优胜美地、PHP 5.5.20、Apache 2.4.9

并按照以下步骤从（http://www.akadia.com/services/ssh_test_certificate.html）

cd /etc/apache2/
sudo mkdir certs                                        
cd certs                                                
sudo openssl genrsa -des3 -out server.key 1024          
sudo openssl req -new -key server.key -out server.csr
  Country Name (2 letter code) [GB]:US
  State or Province Name (full name) [Berkshire]:California 
  Locality Name (eg, city) [Newbury]:LA
  Organization Name (eg, company) [My Company Ltd]:Company
  Organizational Unit Name (eg, section) []:
  Common Name (eg, your name or your server's hostname) []:dev.test.local
  Email Address []:username@gmail.com
  Please enter the following 'extra' attributes
  to be sent with your certificate request
  A challenge password []:
  An optional company name []:
sudo cp server.key server.key.org     
sudo openssl rsa -in server.key.org -out server.key
sudo openssl x509 -req -days 730 -in server.csr -signkey server.key -out server.crt  

接下来，我为我的 apache 配置文件进行了以下设置：

etc/apache2/httpd.conf：

LoadModule ssl_module libexec/apache2/mod_ssl.so
LoadModule socache_shmcb_module libexec/apache2/mod_socache_shmcb.so
Include /private/etc/apache2/extra/httpd-ssl.conf

etc/apache2/extra/httpd-ssl.conf：

Listen 443
SSLPassPhraseDialog  builtin
<VirtualHost _default_:443>
SSLEngine on
Mutex sysvsem default # Added after seeing mutex issues for apache 2.4, http://stackoverflow.com/questions/13969272/apache-sslmutex-issue

etc/apache2/extra/httpd-vhosts.conf：

<VirtualHost *:443>
    ServerName dev.test.local
    DocumentRoot "/Users/username/Sites/test/public"
    <Directory "/Users/username/Sites/test/public">
         Options Indexes FollowSymLinks MultiViews
         AllowOverride All
         Order allow,deny
         allow from all
    </Directory>
    SSLEngine on       
    SSLCertificateFile    /etc/apache2/certs/server.crt
    SSLCertificateKeyFile /etc/apache2/certs/server.key
</VirtualHost>

重新启动并运行 apache 配置测试后，看起来好像没有问题：

sudo apachectl restart
sudo apachectl configtest
[Tue Jan 06 13:56:01.480270 2015] [so:warn] [pid 31636] AH01574: module php5_module is already loaded, skipping
Syntax OK

非常感谢帮助，如果需要，我很乐意提供更多信息。