[BUG] state file.patch pretend to apply malformed patch

[msciciel]

Description
If patch file provided for file.patch state is malformed then state returns Patch was already applied but patch is not applied.

          ID: patch_example
    Function: file.patch
        Name: /tmp/example
      Result: True
     Comment: Patch was already applied
     Started: 12:20:50.953163
    Duration: 61.558 ms
     Changes:

Setup
/srv/salt/example.sls:

patch_example:
  file.patch:
    - name: /tmp/example
    - source: salt://example.patch

/srv/salt/example.patch:

--- /tmp/example        2021-03-15 12:20:20.698463273 +0000
+++ /tmp/example.new    2021-03-15 12:01:26.620433384 +0000
@@ -172,6 +172,7 @@ malformed patch
+EXAMPLE PATCH
+EXAMPLE PATCH
+EXAMPLE PATCH
+EXAMPLE PATCH

[root@1566f989189e ~]# cat /tmp/example
EXAMPLE FILE TO PATCH

/tmp/example

EXAMPLE FILE TO PATCH

Steps to Reproduce the behavior

yum install -y patch
salt-call --local state.sls example -l debug

[DEBUG   ] file.managed: {'changes': {'diff': '--- \n+++ \n@@ -0,0 +1,4 @@\n+--- /tmp/example\t2021-03-15 12:20:20.698463273 +0000\n++++ /tmp/example.new\t2021-03-15 12:01:26.620433384 +0000\n+@@ -172,6 +172,19 @@ malformed patch\n++EXAMPLE PATCH\n'}, 'comment': 'File /tmp/__salt.tmp.vkktza9o updated', 'name': '/tmp/__salt.tmp.vkktza9o', 'result': True}
[DEBUG   ] LazyLoaded cmd.run_all
[INFO    ] Executing command /usr/bin/patch in directory '/root'
[ERROR   ] Command '/usr/bin/patch' failed with return code: 2
[ERROR   ] stdout: patching file /tmp/__salt.tmp.pj5ysvms (read from /tmp/example)
[ERROR   ] stderr: /usr/bin/patch: **** unexpected end of file in patch
[ERROR   ] retcode: 2
[INFO    ] Executing command /usr/bin/patch in directory '/root'
[INFO    ] Patch was already applied

Expected behavior
It would be nice to return error when patch is malformed and can not be applied:

          ID: patch_example
    Function: file.patch
        Name: /tmp/example
      Result: False
     Comment: /usr/bin/patch: **** malformed patch at line 7:
     Started: 12:33:44.915605
    Duration: 59.202 ms
     Changes:

Versions Report

salt --versions-report

Salt Version:
          Salt: 3002.5

Dependency Versions:
          cffi: Not Installed
      cherrypy: Not Installed
      dateutil: 2.6.1
     docker-py: Not Installed
         gitdb: Not Installed
     gitpython: Not Installed
        Jinja2: 2.10.1
       libgit2: Not Installed
      M2Crypto: 0.35.2
          Mako: Not Installed
       msgpack: 0.6.2
  msgpack-pure: Not Installed
  mysql-python: Not Installed
     pycparser: Not Installed
      pycrypto: Not Installed
  pycryptodome: Not Installed
        pygit2: Not Installed
        Python: 3.6.8 (default, Aug 24 2020, 17:57:11)
  python-gnupg: Not Installed
        PyYAML: 3.12
         PyZMQ: 19.0.0
         smmap: Not Installed
       timelib: Not Installed
       Tornado: 4.5.3
           ZMQ: 4.3.4

System Versions:
          dist: centos 8
        locale: UTF-8
       machine: x86_64
       release: 3.10.0-1160.15.2.el7.x86_64
        system: Linux
       version: CentOS Linux 8

Additional context
Add any other context about the problem here.

[msciciel]

If proposed solution is acceptable I will fulfill requirements for the pull request.

[danielrobbins]

@msciciel Thank your for your PR. I have reviewed it, and added a comment with suggested minor changes. If these changes look good to you, please submit an updated PR and I will then support having this fix added to salt.