What version are you running?
0.7.6 from the RHEL EPEL

yum info RBTools.noarch

Loaded plugins: changelog, langpacks, product-id, rhnplugin, search-disabled-repos, subscription-manager, versionlock

Note Spacewalk repositories are not listed below. You must run this command as root to access Spacewalk repositories.

Installed Packages

Name        : RBTools

Arch        : noarch

Version     : 0.7.6

Release     : 1.el7

Size        : 1.5 M

Repo        : installed

From repo   : epel-llnl

Summary     : Tools for use with ReviewBoard

URL         : http://www.review-board.org

License     : MIT

Description : RBTools provides client tools for interacting with a ReviewBoard

            : code-review server.
What steps will reproduce the problem?

Generate a very code change (in our case, ~14,000 lines of output from svn diff)
Check the code change in to SVN.
Use rbt diff to list the change or rbt post to post a ReviewBoard review.


What is the expected output? What do you see instead?
In the case of rbt diff, I expect to see a full diff. In the case of rbt post, I expect to be able to successfully post a new review or update an existing review.
Instead, the output is truncated with errors messages from diff.
What operating system are you using?
Red Hat Enterprise Linux Server release 7.3 (Maipo)

Attach the debug out from the command.

$ rbt diff --debug 19868
>>> RBTools 0.7.6
>>> Python 2.7.5 (default, Aug  2 2016, 04:20:16) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-4)]
>>> Running on Linux-3.10.0-514.el7.x86_64-x86_64-with-redhat-7.3-Maipo
>>> Home = /home/cleary3
>>> Current directory = /home/cleary3/7.5-tmp
>>> Checking for a Subversion repository...
>>> Running: svn --non-interactive info
>>> Running: diff --version
>>> Running: svn --non-interactive --version -q
>>> repository info: Path: svn+ssh://jenova/var/svn/hpss, Base path: /branches/7.5, Supports changesets: False
>>> Making HTTP GET request to https://hpss-dev.clearlake.ibm.com/reviewboard/api/
>>> Running: svn --non-interactive log --xml -r 19868 -l 1
>>> Running: svn --non-interactive info
>>> Running: diff --version
>>> Running: svn --non-interactive --version -q
>>> repository info: Path: svn+ssh://jenova/var/svn/hpss, Base path: /branches/7.5, Supports changesets: False
>>> Running: svn --non-interactive diff --diff-cmd=diff --notice-ancestry -r 19867:19868
Failed to execute command: ['svn', '--non-interactive', u'diff', u'--diff-cmd=diff', u'--notice-ancestry', u'-r', u'19867:19868']
['Index: include/mps_metadata.h\n', '===================================================================\n',
.
.
.
'diff: write failed\n', "svn: E200012: 'diff' returned 2\n"]



Please provide any additional information below.
Running the SVN diff by hand succeeds:

$ svn --non-interactive diff --diff-cmd=diff --notice-ancestry -r 19867:19868 | wc -l
14323
$ svn --non-interactive diff --diff-cmd=diff --notice-ancestry -r 19867:19868 > /dev/null
$ echo $?
0