First effort at doing make like variable expansion so we don't have to patch when file locations change

etc/dkimpy-milter.openrc.in

@@ -0,0 +1,54 @@
+#!/sbin/openrc-run
+# Copyright 1999-2019 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+CONFFILE="@SYSCONFDIR@/${RC_SVCNAME}.conf"
+required_files="${CONFFILE}"
+
+command="@SBINDIR@/dkimpy-milter"
+pidfile="@RUNSTATEDIR@/${RC_SVCNAME}.pid"
+command_args="-P ${pidfile} -x ${CONFFILE}"
+extra_commands="checkconfig"
+
+depend() {
+	use dns logger net
+	before mta
+}
+
+checkconfig() {
+	#
+	# The dkimpy-milter.conf man page says,
+	#
+	#   For parameters that are Boolean in nature, only the first byte
+	#   of the value is processed... For negative values, the following
+	#   are accepted: "F", "f", "N", "n", "0".'
+	#
+	if @GREP@ '^[[:space:]]*Background[[:space:]]\+[FfNn0]' "${CONFFILE}" \
+		>/dev/null 2>&1; then
+		eend 1 "${RC_SVCNAME} cannot run in the foreground!"
+	fi
+	if ! "${command}" -n "${command_args}"; then
+		eend 1 "${RC_SVCNAME} configuration check failed"
+	fi
+}
+
+start_pre() {
+	# If this isn't a restart, make sure that the user's config isn't
+	# busted before we try to start the daemon (this will produce
+	# better error messages than if we just try to start it blindly).
+	#
+	# If, on the other hand, this *is* a restart, then the stop_pre
+	# action will have ensured that the config is usable and we don't
+	# need to do that again.
+	if [ "${RC_CMD}" != "restart" ]; then
+		checkconfig || return $?
+	fi
+}
+
+stop_pre() {
+	# If this is a restart, check to make sure the user's config
+	# isn't busted before we stop the running daemon.
+	if [ "${RC_CMD}" = "restart" ]; then
+		checkconfig || return $?
+	fi
+}

setup.py

@@ -17,10 +17,60 @@
     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA."""
 
 from setuptools import setup
+import distutils.cmd
+import distutils.log
+import sys
 import os
+import subprocess
 
 description = "Domain Keys Identified Mail (DKIM) signing/verifying milter for Postfix/Sendmail."
 
+class FileMacroExpand(distutils.cmd.Command):
+    description = "Expand @@ variables in input files, simlar to make macros."
+    user_options = [
+        ('sysconfigdir=', 'e', 'Specify configuration directory. [/usr/local/etc]'),
+        ('sbindir=', 's', 'Specify system binary directory. [/usr/local/sbin]'),
+        ('bindir=', 'b', 'Specify binary directory. [/usr/loca/bin]'),
+        ('rundir=', 'r', 'Specify run state directory. [/run]'),
+    ]
+
+    def initialize_options(self):
+        self.sysconfigdir = '/usr/local/etc'
+        self.sbindir = '/usr/local/sbin'
+        self.bindir = '/usr/local/bin'
+        self.rundir = '/run'
+        # For this option, we find the system grep, wherever it is and use it,
+        # no override provided.
+        self.grep = subprocess.check_output(["which", "grep"]).decode()[:-1]
+
+    def finalize_options(self):
+        pass
+
+    def run(self):
+        files = ['etc/dkimpy-milter.openrc',]
+        for infile in files:
+            outfile = ''
+            filein = open(infile + '.in')
+            for line in filein:
+                for function in ["@SYSCONFDIR@", "@SBINDIR@", "@BINDIR@", "@RUNSTATEDIR@", "@GREP@"]:
+                    splitline = line.split(function)
+                    if len(splitline) > 1:
+                        if function == "@SYSCONFDIR@":
+                            line = splitline[0] + self.sysconfigdir + splitline[1]
+                        elif function == "@SBINDIR@":
+                            line = splitline[0] + self.sbindir + splitline[1]
+                        elif function == "@BINDIR@":
+                            line = splitline[0] + self.bindir + splitline[1]
+                        elif function == "@RUNSTATEDIR@":
+                            line = splitline[0] + self.rundir + splitline[1]
+                        elif function == "@GREP@":
+                            line = splitline[0] + self.grep + splitline[1]
+                outfile += line
+            out = open(infile, 'w')
+            for line in outfile:
+                out.write(line)
+            out.close()
+
 kw = {}  # Work-around for lack of 'or' requires in setuptools.
 try:
     import dns
@@ -62,5 +112,8 @@ setup(
         ['system/dkimpy-milter.service']),(os.path.join('etc', 'init.d'),
         ['system/dkimpy-milter'])],
     zip_safe = False,
+    cmdclass={
+        'expand': FileMacroExpand,
+    },
     **kw
 )