i think i might have something that works here...

bootsync.py

@@ -65,7 +65,7 @@ class BootSync(object):
                     self.schema = url.read()
             self.schema = etree.XMLSchema(etree.XML(self.schema))
             self.schema.assertValid(self.xml)
-        return()
+        return(None)
 
     def chkMounts(self, dryrun = False):
         if not dryrun:
@@ -87,20 +87,20 @@ class BootSync(object):
                                            stderr = devnull)
                         elif c.returncode == 32:  # Already mounted
                             pass
-        return()
+        return(None)
 
     def chkReboot(self):
         self._getInstalledKernel()
         if not self.kernelFile:
-            return()  # No isKernel="true" was specified in the config.
+            return()  # No 'isKernel="true"' attribute was specified in the config.
         if self.installedKernVer != self.currentKernVer:
             self.RequireReboot = True
             # TODO: logger instead?
             print(('NOTE: REBOOT REQUIRED. '
                    'New kernel is {0}. '
                    'Running kernel is {1}.').format(self.installedKernVer,
-                                                   self.currentKernVer))
-        return()
+                                                    self.currentKernVer))
+        return(None)
 
     def getBlkids(self):
         cmd = ['/usr/bin/blkid',
@@ -129,12 +129,10 @@ class BootSync(object):
         cmd = ['/usr/bin/findmnt',
                '--json',
                '-T', '/boot']
-        # if os.geteuid() != 0:
-        #     cmd.insert(0, 'sudo')
         c = subprocess.run(cmd,
                            stdout = subprocess.PIPE)
         self.dummy_uuid = self.blkids[json.loads(c.stdout.decode('utf-8'))['filesystems'][0]['source']]
-        return()
+        return(None)
 
     def getChecks(self):
         # Get the default hashtype (if one exists)
@@ -155,7 +153,7 @@ class BootSync(object):
                     if rel_fpath not in self.syncs:
                         self.syncs[rel_fpath] = []
                     self.syncs[rel_fpath].append(mount)
-        return()
+        return(None)
 
     def sync(self, dryrun = False, *args, **kwargs):
         if not dryrun:
@@ -206,7 +204,6 @@ class BootSync(object):
                                         shutil.copy2(bootsource, bootfile)
         return()
 
-
     def writeConfs(self, dryrun = False, *args, **kwargs):
         if not dryrun:
             if os.geteuid() != 0:
@@ -231,12 +228,12 @@ class BootSync(object):
                     # If the array is in a degraded state, this will still let us at LEAST boot.
                     line = re.sub(r'\s+--hint=[\'"]?mduuid/[a-f0-9]{32}[\'"]?', '', line)
                     line = re.sub(r'^(\s*set\s+root=){0}$'.format(self.dummy_uuid),
-                                  self.blkids[disk],
+                                  r'\g<1>{0}'.format(self.blkids[disk]),
                                   line)
                     line = re.sub(r'(?<!\=UUID\=){0}'.format(self.dummy_uuid),
                                   self.blkids[disk],
                                   line)
-                    line = re.sub('(^\s*|\s+)/boot', '', line)
+                    line = re.sub(r'(^\s*|\s+)/boot', '', line)
                     f.write('{0}\n'.format(line))
         return()
 
@@ -252,7 +249,7 @@ class BootSync(object):
         _hash = hasher()
         with open(fpathname, 'rb') as fh:
             _hash.update(fh.read())
-        return (_hash.hexdigest())
+        return(_hash.hexdigest())
 
     def _getRunningKernel(self):
         _vers = []

bootsync.xsd

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
-           targetNamespace="http://git.square-r00t.net/OpTools/tree/sys/BootSync/"
-           xmlns="http://git.square-r00t.net/OpTools/tree/sys/BootSync/"
-           xmlns:bootsync="http://git.square-r00t.net/OpTools/tree/sys/BootSync/"
+           targetNamespace="http://git.square-r00t.net/BootSync/"
+           xmlns="http://git.square-r00t.net/BootSync/"
+           xmlns:bootsync="http://git.square-r00t.net/BootSync/"
            elementFormDefault="qualified"
            attributeFormDefault="unqualified">
 
@@ -120,4 +120,4 @@
             </xs:sequence>
         </xs:complexType>
     </xs:element>
-</xs:schema>
+</xs:schema>

sample.config.xml

@@ -5,8 +5,8 @@
 SEE prep.txt FOR WHAT MUST BE DONE BEFORE RUNNING BOOTSYNC.
 -->
 <bootsync xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-          xmlns="http://git.square-r00t.net/OpTools/tree/sys/BootSync/"
-          xsi:schemaLocation="http://git.square-r00t.net/OpTools/plain/sys/BootSync/bootsync.xsd">
+          xmlns="http://git.square-r00t.net/BootSync/"
+          xsi:schemaLocation="http://git.square-r00t.net/BootSync/plain/bootsync.xsd">
     <!-- The actual EFI System Partitions (ESP). At least two are required. -->
     <!-- Each drive should be prepared ahead of time with efibootmgr and grub-install (see prep.txt). -->
     <partitions>
@@ -84,7 +84,10 @@ SEE prep.txt FOR WHAT MUST BE DONE BEFORE RUNNING BOOTSYNC.
         <path source="/usr/lib/grub/x86_64-efi" target="grub/x86_64-efi" pattern="^.*\.(mod|lst|sh)$"/>
         <!-- And these are ISO files, in case you're like me and do loop mounting in Grub for rescue situations.
              (e.g. https://wiki.archlinux.org/index.php/Multiboot_USB_drive#Using_GRUB_and_loopback_devices) -->
+        <!-- You can do this yourself easily via https://git.square-r00t.net/RelChk/ -->
         <!-- <path hashtype="false" source="/boot/iso" target="iso" pattern="^.*\.(iso|img)$"/> -->
-        <path hashtype="md5" source="/boot/iso" target="iso" pattern=".*"/>
+        <!-- I use RelChk (see above), so I also copy over the .json files that contain easily accessible information
+             about the ISO images. -->
+        <path hashtype="md5" source="/boot/iso" target="iso" pattern="^.*\.(iso|img|json)$"/>
     </syncPaths>
 </bootsync>