Add sympy to known_third_party in .isort.cfg

I have installed the newest master of SymPy as editable package. So `isort` thinks it's one of our libraries. With this config SymPy is declared as a third party dependency.

Add sympy to known_third_party in .isort.cfg
I have installed the newest master of SymPy as editable package. So `isort` thinks it's one of our libraries. With this config SymPy is declared as a third party dependency.
2c478a3b · Stephan Seitz · 3f5fe292 · 2c478a3b
Commit 2c478a3b authored 5 years ago by Stephan Seitz
--- a/.isort.cfg
+++ b/.isort.cfg
@@ -2,3 +2,4 @@
 line_length=100
 balanced_wrapping=True
 multi_line_output=4
+known_third_party=sympy