Fix tz.gettz() not returning local time for empty string

nocache checks the gettz(name) parameter with if not name and tries to get the local time from the TZ environment variable. When the environment variable does not exist, it only checked for name is None, skipping the logic that searches for the local time tzfile when passed an empty string.

Fixes #925, #926

changelog.d/1024.misc.rst

@@ -0,0 +1,2 @@
+Fixed tz.gettz() not returning local time when passed an empty string.
+Reported by @labrys (gh issues #925, #926). Fixed by @ffe4 (gh pr #1024)

dateutil/test/test_tz.py

@@ -1077,6 +1077,12 @@ def testGettzCacheTzLocal(self):
         local2 = tz.gettz()
 
         assert local1 is not local2
+
+    def test_gettz_same_result_for_none_and_empty_string(self):
+        local1 = tz.gettz()
+        local2 = tz.gettz("")
+
+        assert local1 == local2
 
 
 @pytest.mark.gettz

dateutil/tz/tz.py

@@ -1596,7 +1596,7 @@ def nocache(name=None):
                     name = os.environ["TZ"]
                 except KeyError:
                     pass
-            if name is None or name == ":":
+            if not name or name == ":":
                 for filepath in TZFILES:
                     if not os.path.isabs(filepath):
                         filename = filepath