don't allow crs in the code

triggered by this slipping into quantum, now that we have more windows
developers we should ensure that \r\n doesn't land in the code as
a line ending. This check prevents it.

Change-Id: I0a82be0e74915d3c3c25203db110d279580c148b

HACKING.rst

@@ -9,6 +9,7 @@ Nova Style Commandments
 General
 -------
 - Put two newlines between top-level code (funcs, classes, etc)
+- Use only UNIX style newlines ("\n"), not Windows style ("\r\n")
 - Put one newline between methods in classes and anywhere else
 - Long lines should be wrapped in parentheses
   in preference to using a backslash for line continuation.

tools/hacking.py

@@ -359,6 +359,19 @@ def nova_docstring_multiline_end(physical_line):
             return (pos, "N403: multi line docstring end on new line")
 
 
+def nova_no_cr(physical_line):
+    r"""Check that we only use newlines not cariage returns.
+
+    Okay: import os\nimport sys
+    # pep8 doesn't yet replace \r in strings, will work on an
+    # upstream fix
+    N901 import os\r\nimport sys
+    """
+    pos = physical_line.find('\r')
+    if pos != -1 and pos == (len(physical_line) - 2):
+        return (pos, "N901: Windows style line endings not allowed in code")
+
+
 FORMAT_RE = re.compile("%(?:"
                             "%|"           # Ignore plain percents
                             "(\(\w+\))?"   # mapping key