Convert Python 2 idioms to Python 2/3-compatible ones.

- convert print, StringIO, except as, octals, izip
- convert print statement to print function
- convert StringIO to six.StringIO
  - remove usage of csv reader in Spec, in favor of simple regex
  - csv reader only does byte strings
- convert 0755 octal literals to 0o755
- convert `except Foo, e` to `except Foo as e`
- fix a few places `str` is used.
  - may need to switch everything to str later.
- convert iteritems usages to use six.iteritems
- fix urllib and HTMLParser
- port metaclasses to use six.with_metaclass
- More octal literal conversions for Python 2/3
- Fix a new octal literal.
- Convert `basestring` to `six.string_types`
- Convert xrange -> range
- Fix various issues with encoding, iteritems, and Python3 semantics.
- Convert contextlib.nested to explicitly nexted context managers.
- Convert use of filter() to list comprehensions.
- Replace reduce() with list comprehensions.
-  Clean up composite: replace inspect.ismethod() with callable()
- Python 3 doesn't have "method" objects; inspect.ismethod returns False.
- Need to use callable in Composite to make it work.
- Update colify to use future division.
- Fix zip() usages that need to be lists.
- Python3: Use line-buffered logging instead of unbuffered.
- Python3 raises an error with unbuffered I/O
  - See https://bugs.python.org/issue17404

lib/spack/llnl/util/tty/log.py

@@ -165,8 +165,12 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         self.p.join(60.0)  # 1 minute to join the child
 
     def _spawn_writing_daemon(self, read, input_stream):
-        # Parent: read from child, skip the with block.
-        read_file = os.fdopen(read, 'r', 0)
+        # This is the Parent: read from child, skip the with block.
+
+        # Use line buffering (3rd param = 1) since Python 3 has a bug
+        # that prevents unbuffered text I/O.
+        read_file = os.fdopen(read, 'r', 1)
+
         with open(self.filename, 'w') as log_file:
             with keyboard_input(input_stream):
                 while True: