SaltRenderError when reactor gets salt.managed diff?

Description of Issue/Question

A salt.manage state copies a file.

Is the reactor unable to parse salt.managed diff?

Setup

This is minionconf.sls, it copies a file minionconf.conf to the minion:

minionconf_file:
  file.managed:
    - source: salt://minionconf.conf
    - name: /salt/conf/minion.d/minionconf.conf
    - fire_event: True

This is file minionconf.conf

ping_interval: 90
random_startup_delay: 30

This is the minionconf_reactor.sls

minionconf_reaction:
  runner.minionconf_runner.main:
    - arg:
      - {{ data }}

This is the error:

2019-02-20 16:33:20,957 [salt.utils.reactor:101 ][ERROR   ][24341] Failed to render "/srv/salt/reactor/minionconf_reactor.sls":
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/salt/utils/reactor.py", line 92, in render_reaction
    data=data)
  File "/usr/lib/python2.7/dist-packages/salt/state.py", line 383, in render_template
    **kwargs)
  File "/usr/lib/python2.7/dist-packages/salt/template.py", line 93, in compile_template
    ret = render(input_data, saltenv, sls, **render_kwargs)
  File "/usr/lib/python2.7/dist-packages/salt/renderers/yaml.py", line 59, in render
    raise SaltRenderError(exc)
SaltRenderError: while parsing a flow mapping
  in "<unicode string>", line 4, column 466:
     ...  u'__run_num__': 0, u'changes': {u'diff': u'--- \n+++ \n@@ -1 +1 ...
                                         ^
expected ',' or '}', but got ':'
  in "<unicode string>", line 4, column 538:
     ... ping_interval: 1\n+ping_interval: 90\n+random_startup_delay: 30\ ...

Workaround

Added show_changes: False to file.managed

Versions Report

salt-run --versions-report
Salt Version:
Salt: 2018.3.3

Dependency Versions:
cffi: 0.8.6
cherrypy: Not Installed
dateutil: 2.2
docker-py: Not Installed
gitdb: 0.5.4
gitpython: 0.3.2 RC1
ioflo: Not Installed
Jinja2: 2.9.4
libgit2: Not Installed
libnacl: Not Installed
M2Crypto: Not Installed
Mako: Not Installed
msgpack-pure: Not Installed
msgpack-python: 0.4.2
mysql-python: 1.2.3
pycparser: 2.10
pycrypto: 2.6.1
pycryptodome: Not Installed
pygit2: Not Installed
Python: 2.7.9 (default, Sep 25 2018, 20:42:16)
python-gnupg: Not Installed
PyYAML: 3.11
PyZMQ: 14.4.0
RAET: Not Installed
smmap: 0.8.2
timelib: Not Installed
Tornado: 4.2.1
ZMQ: 4.0.5

System Versions:
dist: debian 8.11
locale: UTF-8
machine: x86_64
release: 3.16.0-6-amd64
system: Linux
version: debian 8.11

Start with salt/utils/reactor.py at render_reaction and follow the call into salt/template.py and salt/renderers/yaml.py. Reproduce the provided file.managed and reactor SLS with show_changes enabled; done means the reactor renders the event data without SaltRenderError while preserving the diff.