title: Pyflakes "invalid syntax" and print function's variable in curly braces
body: <p>I has Sublime Text 3 installed, SublimeLinter plugin and pyflakes linter.
  In the pip pyflakes version is 1.6.0. OS win 7 x86.</p>
  
  <pre><code>my_name = 'Name'
  print(f"My name is {my_name}.")
  </code></pre>
  
  <p>And here is the error:</p>
  
  <pre><code>SublimeLinter: pyflakes output:
  ex3.py:9:30: invalid syntax
  print(f"My name is {my_name}.")
                               ^ 
  </code></pre>
  
  <p>Also, with this construction i have no errors:</p>
  
  <pre><code>print("My name is {}.".format(my_name))
  </code></pre>
  
  <p>Code is runing just fine, but why pyflakes gives me this error then? Is it pyflakes issue or what?</p>