Fix tz.gettz() behavior with empty string

The documented behavior of the function is to return a local time zone
when the argument is None or an empty string.

This was working if the TZ environment variable was set, but not working
otherwise.

Fixes #925, #926

3 files changed, 12 insertions, 1 deletions

diff --git a/changelog.d/1024.misc.rst b/changelog.d/1024.misc.rst
new file mode 100644
index 0000000..d55f738
--- /dev/null
+++ b/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)
\ No newline at end of file
diff --git a/dateutil/test/test_tz.py b/dateutil/test/test_tz.py
index 6cd8ea0..e5e4772 100644
--- a/dateutil/test/test_tz.py
+++ b/dateutil/test/test_tz.py
@@ -1080,6 +1080,15 @@ class GettzTest(unittest.TestCase, TzFoldMixin):
 
 
 @pytest.mark.gettz
+def test_gettz_same_result_for_none_and_empty_string():
+    local_from_none = tz.gettz()
+    local_from_empty_string = tz.gettz("")
+    assert local_from_none is not None
+    assert local_from_empty_string is not None
+    assert local_from_none == local_from_empty_string
+
+
+@pytest.mark.gettz
 @pytest.mark.parametrize('badzone', [
     'Fake.Region/Abcdefghijklmnop',  # Violates several tz project name rules
 ])
diff --git a/dateutil/tz/tz.py b/dateutil/tz/tz.py
index af81e88..320708d 100644
--- a/dateutil/tz/tz.py
+++ b/dateutil/tz/tz.py
@@ -1596,7 +1596,7 @@ def __get_gettz():
                     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