remove usage of planarity and clean up reqs file

Author: tomvanmele

requirements.txt

@@ -1,20 +1,15 @@
 # flake8: noqa
-cython
 # ezdxf
 imageio <= 2.6; python_version < '3.5'
 imageio >= 2.7; python_version >= '3.5'
 jsonschema >= 4.17, < 4.18
-# laspy
 matplotlib >= 2.2, < 3.0; python_version >= '2.7' and python_version < '3.0'
 matplotlib >= 2.2, < 3.1; python_version >= '3.5' and python_version <= '3.7' and sys_platform == 'win32'
 matplotlib >= 3.1; python_version >= '3.8' and sys_platform == 'win32'
 matplotlib >= 2.2; python_version >= '3.5' and sys_platform != 'win32'
 networkx
-# numba
 numpy >= 1.15.4
 pillow
-# planarity ; sys_platform != 'win32'
-pycollada
 schema
 scipy >= 1.1
 sympy

src/compas/datastructures/network/planarity.py

@@ -192,12 +192,12 @@ def network_is_planar(network):
 
     """
     try:
-        import planarity
+        import networkx as nx
     except ImportError:
-        print("Planarity is not installed.")
+        print("NetworkX is not installed. Get NetworkX at https://networkx.github.io/.")
         raise
 
-    return planarity.is_planar(list(network.edges()))
+    return nx.is_planar(network.to_networkx())
 
 
 def network_is_planar_embedding(network):