fix(mtnetwork): add import check

try to import HyPhy before use
in transmission_network.fit_degree_distribution

closes veg#40

Author: FynnFreyer

hivclustering/mtnetwork.py

@@ -2509,8 +2509,8 @@ def fit_degree_distribution(self, degree_option=None, hy_instance=None):
             try:
                 import hppy as hy
             except ImportError:
-                raise ImportError("Optional dependencies not found. please install the 'edgefiltering' extras to use this function: pip install hivclustering[edgefiltering]")
-
+                raise ImportError(
+                    "Optional dependencies not found. Please install the 'edgefiltering' extras to use this function: pip install hivclustering[edgefiltering]")
             hy_instance = hy.HyphyInterface()
 
         script_path = os.path.realpath(__file__)