Issue #18873: IDLE, 2to3, and the findnocoding.py script now detect Python
source code encoding only in comment lines.
diff --git a/Tools/scripts/findnocoding.py b/Tools/scripts/findnocoding.py
index e49fc42..838e573 100755
--- a/Tools/scripts/findnocoding.py
+++ b/Tools/scripts/findnocoding.py
@@ -32,13 +32,13 @@
                          "no sophisticated Python source file search will be done.")
 
 
-decl_re = re.compile(r"coding[=:]\s*([-\w.]+)")
+decl_re = re.compile(r'^[ \t\f]*#.*coding[:=][ \t]*([-\w.]+)', re.ASCII)
 
 def get_declaration(line):
-    match = decl_re.search(line)
+    match = decl_re.match(line)
     if match:
         return match.group(1)
-    return ''
+    return b''
 
 def has_correct_encoding(text, codec):
     try: