Raw strings create syntax error when last character is a backslash (\).  
This problem seems to exist across all versions of python (that I have access to)

Sample Code:
-------------------------------------------------------------
Under Windows Python 2.7.3
Works Correctly:
>>> test = r'C:\Program Files\^%(x86)\Internet Explorer\iexplore.exe'
>>> print test
C:\Program Files\^%(x86)\Internet Explorer\iexplore.exe

Fails because last character is backslash
>>> test = r'C:\Program Files\^%(x86)\Internet Explorer\'
SyntaxError: EOL while scanning string literal
-------------------------------------------------------------
Under Linux Python 2.7.12
Works Correctly
>>> j=r"\n"
>>> print j
\n

Fails because last character is backslash
>>> j=r"n\"
SyntaxError: EOL while scanning string literal

Works correctly:
>>> j=r"n\n"
>>> print j
n\n

Works correctly:
>>> j=r"n\\"
>>> print j
n\\
-------------------------------------------------------------
Under Linux Python 3.5.2
Fails because last character is backslash
>>> j=r"\'
  File "<stdin>", line 1
    j=r"\'
         ^
SyntaxError: EOL while scanning string literal
-------------------------------------------------------------

This is defined behavior, not a bug.  See the end of the section on string literals: https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals