Fix tz.gettz() not returning local time for 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 +1077,17 @@ 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.skipif(IS_WIN, reason='requires Unix')
+    def test_gettz_returns_local_time(self):
+        with TZEnvContext('/etc/localtime'):
+            assert tz.gettz() == tz.tzfile('/etc/localtime')
 
 
 @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 name is None or name == "" or name == ":":
                 for filepath in TZFILES:
                     if not os.path.isabs(filepath):
                         filename = filepath