Clean up

lbmpy/phasefield/nphase_nestler.py

 try:
-   import pyximport
-   pyximport.install(language_level=3)
-   from lbmpy.phasefield.simplex_projection import simplex_projection_2d  # NOQA
-except:
+    import pyximport
+
+    pyximport.install(language_level=3)
+    from lbmpy.phasefield.simplex_projection import simplex_projection_2d  # NOQA
+except ImportError:
     try:
         from lbmpy.phasefield.simplex_projection import simplex_projection_2d  # NOQA
-    except:
-        raise ImportError("neither pyximport nor binary module available")
+    except ImportError:
+        raise ImportError("neither pyximport nor binary module simplex_projection_2d available.")
 
 import sympy as sp