rcg: fix module symvers discovery

This makes discovery of the Module.symvers happen at model build time, instead of at build tree creation/configuration.

fixes #33 (closed)

src/epics/util/find_module_symvers

-#!/bin/bash -e
+#!/usr/bin/env python3
 
-MOD=$1
-if [ -z "$MOD" ] ; then
-    echo "Must specify module" >&2
-    exit 1
-fi
+import os
+import sys
+import subprocess
 
-modsym=
+try:
+    modname = sys.argv[1]
+except IndexError:
+    exit("usage: {} <modname>".format(sys.argv[0]))
 
-mbufstat=$(dkms status -m ${MOD})
-if [ ! -z "${mbufstat}" ] ; then
-    mmodvers=`echo ${mbufstat} | awk '{print $2}' | sed 's/.$//'`
-    mkvers=`echo ${mbufstat} | awk '{print $3}' | sed 's/.$//'`
-    march=`echo ${mbufstat} | awk '{print $4}' | sed 's/.$//'`
-    mtestpath="/var/lib/dkms/${MOD}/${mmodvers}/${mkvers}/${march}/Module.symvers"
-    if [ -f $mtestpath ] ; then
-	modsym=$mtestpath
-    fi
-else
-    mtestpath="/var/cache/${MOD}/Module.symvers"
-    if [ -f $mtestpath ] ; then
-	modsym=$mtestpath
-    fi
-fi
+uname = os.uname()
+modstat = subprocess.run(
+    ['dkms', '-k', uname.release, 'status', modname],
+    capture_output=True, text=True,
+)
+if modstat.returncode == 0 and modstat.stdout:
+    modstat = modstat.stdout.split(':')[0].split(', ')
+    if len(modstat) >= 4:
+        modvers = modstat[1]
+        mkvers = modstat[2]
+        march = modstat[3]
+        modsym = os.path.join(
+            '/var/lib/dkms',
+            modname,
+            modvers,
+            mkvers,
+            march,
+            'Module.symvers',
+        )
+        if os.path.exists(modsym):
+            print(modsym)
+            exit()
 
-if [ -z "$modsym" ] ; then
-    echo "'$MOD' modsym not found" >&2
-    exit 2
-fi
+modsym = os.path.join('/var/cache', modname, 'Module.symvers')
+if os.path.exists(modsym):
+    print(modsym)
+    exit()
 
-echo ${modsym}
+exit("Module '{}' symvers file could not be found.".format(modname))