MACOSX_DEPLOYMENT_TARGET is not set correctly when building the 2.7.10 sources.  This causes readline to not be included in the build.

This appears to already be fixed in 3.4.3.  I picked up the change to configure.ac from 3.4.3 and it resolved the problem.

I am building on 10.9.5.  In my case MACOSX_DEPLOYMENT_TARGET was chosen as 10.4.

The configuration options I am using are:

./configure --enable-shared

Attaching diffs.

New changeset ee8e4b61d6181f5bfadf6ee3d229f0ebda8a6ae9 by Ned Deily in branch '2.7':
[2.7] Backport macOS universal build and installer fixes from 3.6. (GH-6469)
https://github.com/python/cpython/commit/ee8e4b61d6181f5bfadf6ee3d229f0ebda8a6ae9

Thanks for your suggested patch and my apologies for not replying sooner.  For Python 2.7.15, we have done some housecleaning of old macOS support issues and, as part of ee8e4b61d6181f5bfadf6ee3d229f0ebda8a6ae9 for Issue32726, I have backported the deployment target setting behavior from 3.x, i.e. the deployment target on current systems is now set to the build system's OS level unless overridden by MACOSX_DEPLOYMENT_TARGET= on the configure command or as an environment variable.  So the previous behavior can be forced by:

./configure MACOSX_DEPLOYMENT_TARGET=10.4

As you noted, using a proper value for the deployment target allows things like using the system libedit readline support and standard library support for more recent system calls.