Merge pull request #3451 from dopplershift/tweak-metar-doc

Note text-mode needed for METAR file-like objects

src/metpy/io/metar.py

@@ -348,7 +348,8 @@ def parse_metar_file(filename, *, year=None, month=None):
     ----------
     filename : str or file-like object
         If str, the name of the file to be opened. If `filename` is a file-like object,
-        this will be read from directly.
+        this will be read from directly and needs to be opened in text mode (i.e. ``read()``
+        needs to return a string, not bytes).
     year : int, optional
         Year in which observation was taken, defaults to current year. Keyword-only argument.
     month : int, optional