title: Error installing scrapy
body: <p>I'm trying to install scrapy using the command <code>sudo pip install scrapy</code>, but I'm getting an error message which ends as follows:</p>
  
  <pre><code>build/temp.linux-x86_64-2.7/_openssl.c:429:30: fatal error: openssl/opensslv.h: No such file or directory
      compilation terminated.
      error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
  
      ----------------------------------------
  Command "/usr/bin/python -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-tVcVY7/cryptography/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-zyty58-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /tmp/pip-build-tVcVY7/cryptography/
  </code></pre>
  
  <p>The error seems to be related to OpenSSL, which needs to be installed according to <a href="http://doc.scrapy.org/en/latest/intro/install.html" rel="nofollow">http://doc.scrapy.org/en/latest/intro/install.html</a>. However, if I run <code>sudo apt-get install openssl</code>, I get a message which seems to indicate it is already installed:</p>
  
  <pre><code>Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  openssl is already the newest version (1.0.2g-1ubuntu4.1).
  The following packages were automatically installed and are no longer required:
    linux-headers-4.4.0-21 linux-headers-4.4.0-21-generic linux-headers-4.4.0-22
    linux-headers-4.4.0-22-generic linux-image-4.4.0-21-generic
    linux-image-4.4.0-22-generic linux-image-extra-4.4.0-21-generic
    linux-image-extra-4.4.0-22-generic
  Use 'sudo apt autoremove' to remove them.
  0 upgraded, 0 newly installed, 0 to remove and 135 not upgraded.
  </code></pre>
  
  <p>How can I solve this to install scrapy?</p>