file.replace with prepend_if_not_found prepends backslashes as literals

Problem

file.replace with prepend_if_not_found=True prepends backslashes in repl content as literals, regardless of backslash_literal value

Example

Using repl containing tab

empty file, value is prepended as literal:

# salt-call file.replace /tmp/test pattern='my_content.*' repl='my_content\tnew_content' prepend_if_not_found=True backup=False backslash_literal=False
local:
    ---
    +++
    @@ -0,0 +1 @@
    +my_content\tnew_content
# cat /tmp/test
my_content\tnew_content

same file, replace the pattern, value is replaced with backslashes interpreted:

# salt-call file.replace /tmp/test pattern='my_content.*' repl='my_content\tnew_content' prepend_if_not_found=True backup=False backslash_literal=False
local:
    ---
    +++
    @@ -1 +1 @@
    -my_content\tnew_content
    +my_content new_content
# cat /tmp/test
my_content      new_content

providing not_found_content does not change the behaviour, still prepended as literal:

# salt-call file.replace /tmp/test pattern='my_content.*' repl='my_content\tnew_content' not_found_content='my_content\tnew_content' prepend_if_not_found=True backup=False backslash_literal=False 
local:
    ---
    +++
    @@ -0,0 +1 @@
    +my_content\tnew_content
# cat /tmp/test
my_content\tnew_content

Version:

Salt Version:
           Salt: 2019.2.0

Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: 1.5
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.7.2
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: 0.31.0
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: 1.2.5
      pycparser: Not Installed
       pycrypto: 2.6.1
   pycryptodome: 3.6.1
         pygit2: Not Installed
         Python: 2.7.5 (default, Aug  6 2019, 09:12:32)
   python-gnupg: 0.4.3
         PyYAML: 3.11
          PyZMQ: 15.3.0
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.1.4

System Versions:
           dist: redhat 7.7 Valery Bykovsky
         locale: UTF-8
        machine: x86_64
        release: 3.10.0-962.3.2.lve1.5.24.10.el7.x86_64
         system: Linux
        version: CloudLinux 7.7 Valery Bykovsky

Start by reproducing the documented salt-call file.replace commands, then inspect the file.replace handling for prepend_if_not_found, repl, not_found_content, and backslash_literal. Done means prepended content interprets backslash escapes consistently with replacement content when backslash_literal=False, with coverage for the shown cases.