Raise an exception if no parameter is provided to `retrieve_sam()`

[Peque]

Instead of opening a dialog, which feels weird for a library.

pvlib-python/pvlib/pvsystem.py

Lines 1783 to 1788 in 0a14b27

	elif name is None and path is None:
	import tkinter
	from tkinter.filedialog import askopenfilename
	tkinter.Tk().withdraw()
	csvdata = askopenfilename()

Also, that piece of code is probably not tested?

[wholmgren]

I agree. We could deprecate but I think we should just go ahead with the breaking change. Does anyone reading this rely on this behavior?

[cwhanse]

Likely a holdover from the original port from Matlab. I agree with raising the Exception instead of a dialog.

[mikofski]

I'm okay with breaking change here because a dialog is a user interaction vs a programming interface, so change doesn't break the API, just potential user flow. Either way keep it or not, although lack of testing is probably argument for dumping it

[adriesse]

I have a vague memory of the dialog not working for me when I inadvertently tried to use it a few months ago. Prefer exception to dialog.