Pyephem args missmatch (#381)

* fix for issue #343

Now, passed 'offset' parameter are used instead of it's default value.

* test for issue #343

* solar_position_method passed to basic_chain wasn't used causing
execution of solarposition.get_solarposition with default 'nrel_numpy'
value in all cases.

* Update modelchain.py

doc string fixes for modelchain.basic_chain function

* Update v0.5.1.rst

* Update v0.5.1.rst

* Update v0.5.1.rst

* altitude arg was missing.
Consequentially, pressure was passed to altitude and
 temperature was passed to pressure.

* Test for get_solarposition with method='pyephem'

Should prevent args mismatch described in #374
This function is basically a copy of  test_get_solarposition_no_kwargs modified to call get_solarposition  with method='pyephem'

* Update v0.5.1.rst

* Now we pass keyword arguments instead of positional to be safe and consistent.

* decorate test_get_solarposition_method_pyephem with @requires_ephem

Author: KonstantinTr

docs/sphinx/source/whatsnew/v0.5.1.rst

@@ -14,6 +14,8 @@ Bug fixes
   arg to solarposition.get_solarposition
 * Removed unnecessary calculations of alpha_prime in spa.solar_position_numpy
   and spa.solar_position_loop
+* Fixed args mismatch for solarposition.pyephem call 
+  from solarposition.get_solarposition with method='pyephem'
 
 Enhancements
 ~~~~~~~~~~~~

pvlib/solarposition.py

@@ -105,8 +105,10 @@ def get_solarposition(time, latitude, longitude,
                               pressure, temperature,
                               how='numpy', **kwargs)
     elif method == 'pyephem':
-        ephem_df = pyephem(time, latitude, longitude, pressure, temperature,
-                           **kwargs)
+        ephem_df = pyephem(time, latitude, longitude,
+                           altitude=altitude,
+                           pressure=pressure,
+                           temperature=temperature, **kwargs)
     elif method == 'ephemeris':
         ephem_df = ephemeris(time, latitude, longitude, pressure, temperature,
                              **kwargs)

pvlib/test/test_solarposition.py

@@ -354,6 +354,19 @@ def test_get_solarposition_no_kwargs(expected_solpos):
     assert_frame_equal(expected_solpos, ephem_data[expected_solpos.columns])
 
 
+@requires_ephem
+def test_get_solarposition_method_pyephem(expected_solpos):
+    times = pd.date_range(datetime.datetime(2003, 10, 17, 13, 30, 30),
+                          periods=1, freq='D', tz=golden.tz)
+    ephem_data = solarposition.get_solarposition(times, golden.latitude,
+                                                 golden.longitude,
+                                                 method='pyephem')
+    expected_solpos.index = times
+    expected_solpos = np.round(expected_solpos, 2)
+    ephem_data = np.round(ephem_data, 2)
+    assert_frame_equal(expected_solpos, ephem_data[expected_solpos.columns])
+
+
 def test_nrel_earthsun_distance():
     times = pd.DatetimeIndex([datetime.datetime(2015, 1, 2),
                               datetime.datetime(2015, 8, 2),]