🎨 ppn2ocr: Fix some whitespace code style issues

ppn2ocr

@@ -91,7 +91,6 @@ def make_workspace(ppn, workspace):
     remove_file_grp(mets, 'PRESENTATION')
     remove_file_grp(mets, 'LOCAL')
 
-
     # Duplicate DEFAULT file group into a new file group BEST
     format_ = 'tif'
     file_grp_default = mets.find('//mets:fileGrp[@USE="DEFAULT"]', namespaces=XMLNS)
@@ -117,7 +116,6 @@ def make_workspace(ppn, workspace):
 
     mets.find('//mets:fileSec', namespaces=XMLNS).append(file_grp_best)
 
-
     # Write mets.xml
     mets.write('mets.xml', pretty_print=True)
 
@@ -134,11 +132,13 @@ def make_workspace(ppn, workspace):
 
 
 def validate_ppn(ctx, param, value):
+    """Validate a PPN argument"""
     if not value.startswith('PPN'):
         raise click.BadParameter('PPN must be in format PPNxxxxxxxx')
     else:
         return value
 
+
 @click.command()
 @click.argument('ppn', callback=validate_ppn)
 def ppn2ocr(ppn):