Merge pull request #16 from bgoonz/renovate/astroid-2.x

Update dependency astroid to v2.5.7

Author: bgoonz

learn-python/requirements.txt

@@ -1,4 +1,4 @@
-astroid==2.0.4
+astroid==2.5.7
 atomicwrites==1.1.5
 attrs==18.1.0
 flake8==3.5.0