__xrange()__ was removed in Python 3 in favor of a reworked version of __range()__.
[flake8](http://flake8.pycqa.org) testing of https://github.com/tensorflow/privacy on Python 3.7.1
$ __flake8 . --count --select=E9,F63,F72,F82 --show-source --statistics__
```
./privacy/optimizers/gaussian_query_test.py:65:16: F821 undefined name 'xrange'
for _ in xrange(1000):
^
./research/pate_2018/ICLR2018/rdp_bucketized.py:79:12: F821 undefined name 'xrange'
for i in xrange(n):
^
./research/pate_2018/ICLR2018/rdp_bucketized.py:106:12: F821 undefined name 'xrange'
for i in xrange(n):
^
./research/pate_2018/ICLR2018/rdp_bucketized.py:139:12: F821 undefined name 'xrange'
for i in xrange(n):
^
4 F821 undefined name 'xrange'
4
```
__E901,E999,F821,F822,F823__ are the "_showstopper_" [flake8](http://flake8.pycqa.org) issues that can halt the runtime with a SyntaxError, NameError, etc. These 5 are different from most other flake8 issues which are merely "style violations" -- useful for readability but they do not effect runtime safety.
* F821: undefined name `name`
* F822: undefined name `name` in `__all__`
* F823: local variable name referenced before assignment
* E901: SyntaxError or IndentationError
* E999: SyntaxError -- failed to compile a file into an Abstract Syntax Tree
