Fix issue with window_length in reno clearsky detection (#221)

* fix bug

* whatsnew

Author: kandersolar

docs/whatsnew/v0.2.3.rst

@@ -10,7 +10,8 @@ Enhancements
 
 Bug Fixes
 ~~~~~~~~~
-
+* :py:func:`pvanalytics.features.clearsky.reno` now correctly passes
+  ``window_length`` to the underlying pvlib function. (:pull:`221`)
 
 Requirements
 ~~~~~~~~~~~~

pvanalytics/features/clearsky.py

@@ -72,7 +72,7 @@ def reno(ghi, ghi_clearsky):
         ghi,
         ghi_clearsky,
         ghi.index,
-        window_length,
+        window_length=window_length,
         lower_line_length=-5*scale_factor,
         upper_line_length=10*scale_factor,
         slope_dev=8*scale_factor