salt-cp - UnicodeEncodeError in files with non-ascii characters

Description of Issue

Using salt-cp to copy a file with non-ascii characters causes a decode error (and an incomplete copy).

Setup

Salt: 2019.2.0

Steps to Reproduce Issue

Setting up for the test...

# mkdir -p /root/test
# cd /root/test
# rm -f /root/test/*
# curl -s https://www.w3.org/2001/06/utf-8-test/UTF-8-demo.html -o utf8.txt

# salt ip-10-0-253-180-centos1 test.ping
ip-10-0-253-180-centos1:
    True

Ensure environment is sane...

# systemctl restart salt-api salt-master
# salt ip-10-0-253-180-centos1 test.ping
ip-10-0-253-180-centos1:
    True

Reproduce issue....

# salt-cp ip-10-0-253-180-centos1 utf8.txt /tmp/

ip-10-0-253-180-centos1:
    The minion function caused an exception: Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/salt/minion.py", line 1607, in _thread_return
        return_data = minion_instance.executors[fname](opts, data, func, args, kwargs)
      File "/usr/lib/python2.7/site-packages/salt/executors/direct_call.py", line 12, in execute
        return func(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/salt/modules/cp.py", line 84, in recv
        fp_.write(data)
    UnicodeEncodeError: 'ascii' codec can't encode characters in position 347-382: ordinal not in range(128)

And from /var/log/salt/master...

2019-06-14 15:29:24,503 [salt.master      :1577][ERROR   ][15675] Received minion error from [ip-10-0-253-180-centos1]: The minion function caused an exception

Versions Report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)

# salt-master --versions
/usr/lib/python2.7/site-packages/salt/scripts.py:102: DeprecationWarning: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date.  Salt will drop support for Python 2.7 in the Sodium release or later.
Salt Version:
           Salt: 2019.2.0

Dependency Versions:
           cffi: 1.6.0
       cherrypy: 5.6.0
       dateutil: 2.8.0
      docker-py: Not Installed
          gitdb: 0.6.4
      gitpython: 1.0.1
          ioflo: Not Installed
         Jinja2: 2.7.2
        libgit2: 0.26.3
        libnacl: Not Installed
       M2Crypto: 0.31.0
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: 2.14
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: 0.26.4
         Python: 2.7.5 (default, Apr  9 2019, 14:30:50)
   python-gnupg: Not Installed
         PyYAML: 3.10
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: 0.9.0
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4

System Versions:
           dist: centos 7.6.1810 Core
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-957.1.3.el7.x86_64
         system: Linux
        version: CentOS Linux 7.6.1810 Core

Start with salt/modules/cp.py and its recv function, where the traceback shows the failure at fp_.write(data). Reproduce the salt-cp command using the provided UTF-8 demo file, then verify that the non-ASCII file is copied completely without a UnicodeEncodeError.