Update README.md

Author: cclauss

README.md

@@ -1,2 +1,10 @@
-# Find-Python-syntax-errors-action
-GitHub action to find Python syntax errors and undefined names
+# GitHub Action to find Python syntax errors and undefined names
+
+$ __flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics__
+
+__E901,E999,F821,F822,F823__ are the "_showstopper_" [flake8](http://flake8.pycqa.org) issues that can halt the runtime with a SyntaxError, NameError, etc. These 5 are different from most other flake8 issues which are merely "style violations" -- useful for readability but they do not effect runtime safety.
+* F821: undefined name `name`
+* F822: undefined name `name` in `__all__`
+* F823: local variable name referenced before assignment
+* E901: SyntaxError or IndentationError
+* E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree