title: how to check if package with specified version is available?
body: <p>For example function <code>available('foobar&gt;=1.1')</code> should check that package <code>foobar</code> is installed and its version is >= 1.1.</p>
  
  <ul>
  <li>There is <code>importlib.util.find_spec</code>, which can check whether module is installed.</li>
  <li>and <code>LooseVersion</code> from <code>distutils.version</code> to compare versions</li>
  </ul>
  
  <p>But how can I parser string like <code>foobar&gt;=1.1</code> and split it into module, version and comparator? </p>
  
  <p>Or, what is more interesting, maybe there is already some standard way to do all these stuff at the same time? <code>pip</code> is probably doing the same thing when it reads packages from <code>requirements.txt</code></p>