Allow skipping of startup resource checks

If the PYTZ_SKIPEXISTSCHECK environment variable is set, pytz
will not confirm the existance of the expected timezone database
files at import time. This improves startup time, but will cause
crashes when the timezone list baked into the pytz release does
not match the timezone database in use.

Patch from Timothy Paine

1 files changed, 7 insertions, 0 deletions

diff --git a/src/pytz/__init__.py b/src/pytz/__init__.py
index c25a1d1..58a678f 100644
--- a/src/pytz/__init__.py
+++ b/src/pytz/__init__.py
@@ -111,6 +111,13 @@ def open_resource(name):
 def resource_exists(name):
     """Return true if the given resource exists"""
     try:
+        if os.environ.get('PYTZ_SKIPEXISTSCHECK', ''):
+            # In "standard" distributions, we can assume that
+            # all the listed timezones are present. As an
+            # import-speed optimization, you can set the
+            # PYTZ_SKIPEXISTSCHECK flag to skip checking
+            # for the presence of the resource file on disk.
+            return True
         open_resource(name).close()
         return True
     except IOError: