Fall back to importing for OpenSSL detection.

Previously, we'd attempted to detect OpenSSL without actually importing, in
order to avoid a runtime penalty for importing `oauth2client`. However, in
some exotic situations, `imp.find_module` can fail even though the import
would be successful.

We tweak to fall back to importing, and add some gross to the corresponding
test.

1 files changed, 26 insertions, 1 deletions

diff --git a/oauth2client/crypt.py b/oauth2client/crypt.py
index ccdda8c..19f9d9f 100644
--- a/oauth2client/crypt.py
+++ b/oauth2client/crypt.py
@@ -38,8 +38,33 @@ class AppIdentityError(Exception):
   pass
 
 
+def _TryOpenSslImport():
+  """Import OpenSSL, avoiding the explicit import where possible.
+
+  Importing OpenSSL 0.14 can take up to 0.5s, which is a large price
+  to pay at module import time. However, it's also possible for
+  ``imp.find_module`` to fail to find the module, even when it's
+  installed. (This is the case in various exotic environments,
+  including some relevant for Google.) So we first try a fast-path,
+  and fall back to the slow import as needed.
+
+  Args:
+    None
+  Returns:
+    None
+  Raises:
+    ImportError if OpenSSL is unavailable.
+
+  """
+  try:
+    _ = imp.find_module('OpenSSL')
+    return
+  except ImportError:
+    import OpenSSL
+
+
 try:
-  _ = imp.find_module('OpenSSL')
+  _TryOpenSslImport()
 
   class OpenSSLVerifier(object):
     """Verifies the signature on a message."""