title: PyCharm show full diff when unittest fails for multiline string?
body: <p>I am writing some Python unit tests using the "unittest" framework and run them in PyCharm. Some of the tests compare a long generated string to a reference value read from a file. If this comparison fails, I would like to see the diff of the two compared strings using PyCharms diff viewer.</p>
  
  <p>So the the code is like this:</p>
  
  <pre><code>    actual = open("actual.csv").read()
      expected = pkg_resources.resource_string('my_package', 'expected.csv').decode('utf8')
      self.assertMultiLineEqual(actual, expected)
  </code></pre>
  
  <p>And PyCharm nicely identifies the test as a failure and provides a link in the results window to click which opens the diff viewer. However, due to how unittest shortens the results, I get results such as this in the diff viewer:</p>
  
  <p>Left side:</p>
  
  <p>'time[57 chars]ercent
  0;1;1;1;1;1;1;1
  0;2;1;3;4;2;3;1
  0;3;[110 chars]32
  '</p>
  
  <p>Right side:</p>
  
  <p>'time[57 chars]ercen
  0;1;1;1;1;1;1;1
  0;2;1;3;4;2;3;1
  0;3;2[109 chars]32
  '</p>
  
  <p>Now, I would like to get rid of all the [X chars] parts and just see the whole file(s) and the actual diff fully visualized by PyCharm.</p>
  
  <p>I tried to look into unittest code but could not find a configuration option to print full results. There are some variables such as maxDiff and _diffThreshold but they have no impact on this print.</p>
  
  <p>Also, I tried to run this in py.test but there the support in PyCharm was even less (no links even to failed test). </p>
  
  <p>Is there some trick using the difflib with unittest or maybe some other tricks with another Python test framework to do this? </p>