Raise if no parameters provided to retrieve_sam() (#770)

Instead of showing up a dialog.

Author: Peque

pvlib/pvsystem.py

@@ -1781,11 +1781,7 @@ def retrieve_sam(name=None, path=None):
         else:
             csvdata = path
     elif name is None and path is None:
-        import tkinter
-        from tkinter.filedialog import askopenfilename
-
-        tkinter.Tk().withdraw()
-        csvdata = askopenfilename()
+        raise ValueError("A name or path must be provided!")
 
     return _parse_raw_sam_df(csvdata)
 

pvlib/test/test_pvsystem.py

@@ -274,6 +274,15 @@ def pvsyst_module_params():
     return module_parameters
 
 
+def test_retrieve_sam_raise_no_parameters():
+    """
+    Raise an exception if no parameters are provided to `retrieve_sam()`.
+    """
+    with pytest.raises(ValueError) as error:
+        pvsystem.retrieve_sam()
+    assert 'A name or path must be provided!' == str(error.value)
+
+
 def test_sapm(sapm_module_params):
 
     times = pd.date_range(start='2015-01-01', periods=5, freq='12H')