Invalid escape sequence warnings

[Harmon758]

A backslash-character pair that is not a valid escape sequence generates a DeprecationWarning since Python 3.6. In Python 3.8 it generates a SyntaxWarning instead.

https://docs.python.org/3.8/whatsnew/3.8.html

https://docs.python.org/3.6/whatsnew/changelog.html, https://bugs.python.org/issue27364, https://hg.python.org/cpython/rev/38802c38cfe1, python/cpython@110b6fe

Python 3.6.8 (tags/v3.6.8:3c6b436a57, Dec 24 2018, 00:16:47) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from wand import image
C:\Program Files\Python36\lib\site-packages\wand\image.py:6921: DeprecationWarning: invalid escape sequence \
  """  # noqa

Changed in version 3.6: Unrecognized escape sequences produce a DeprecationWarning.

Changed in version 3.8: Unrecognized escape sequences produce a SyntaxWarning. In some future version of Python they will be a SyntaxError.

https://docs.python.org/3.8/reference/lexical_analysis.html

https://bugs.python.org/issue32912, python/cpython#9652, python/cpython@6543912

Python 3.8.0b2 (tags/v3.8.0b2:21dd01d, Jul  4 2019, 16:00:09) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from wand import image
C:\Program Files\Python38\lib\site-packages\wand\image.py:6834: SyntaxWarning: invalid escape sequence \
  """Transforms the image using :c:func:`MagickTransformImage`,

[emcconville]

Thanks! The invalid escape sequences were just for sphinx whitespace styling. Simple enough to fix.