bitbake: parse/ConfHandler: Add warning for deprecated whitespace usage

A lack of whitespace around variable assignment operators makes the
files harder to read.

There is a deeper issue in that a "+" character can sometimes be confused
between the variable name and the assignment operator.

Start showing warnings for such usage so we encourage people to use
consistent whitespace which helps with file readability in general.

(Bitbake rev: 24772dd2ae6c0cd11540a260f15065f906fb0997)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/parse/parse_py/ConfHandler.py

@@ -23,7 +23,7 @@ __config_regexp__  = re.compile( r"""
     (?P<var>[a-zA-Z0-9\-_+.${}/~:]*?)
     (\[(?P<flag>[a-zA-Z0-9\-_+.][a-zA-Z0-9\-_+.@/]*)\])?
 
-    \s* (
+    (?P<whitespace>\s*) (
         (?P<colon>:=) |
         (?P<lazyques>\?\?=) |
         (?P<ques>\?=) |
@@ -32,7 +32,7 @@ __config_regexp__  = re.compile( r"""
         (?P<predot>=\.) |
         (?P<postdot>\.=) |
         =
-    ) \s*
+    ) (?P<whitespace2>\s*)
 
     (?!'[^']*'[^']*'$)
     (?!\"[^\"]*\"[^\"]*\"$)
@@ -168,6 +168,8 @@ def feeder(lineno, s, fn, statements, baseconfig=False, conffile=True):
         groupd = m.groupdict()
         if groupd['var'] == "":
             raise ParseError("Empty variable name in assignment: '%s'" % s, fn, lineno);
+        if not groupd['whitespace'] or not groupd['whitespace2']:
+            logger.warning("%s:%s has a lack of whitespace around the assignment: '%s'" % (fn, lineno, s))
         ast.handleData(statements, fn, lineno, groupd)
         return