Given following log snippets, their explanation, and nothing else, explain what failure, if any, occurred during build of this package.

  Snippets are in a format of [X] : [Y], where [X] is a log snippet, and [Y] is the explanation.

  Snippets are delimited with '================'.

  Drawing on information from all snippets, provide a concise explanation of the issue and recommend a solution.

  Explanation of the issue, and recommended solution, should take a handful of sentences.

  Snippets:

  [  File "/usr/lib/python2.7/site-packages/leapp/utils/lock.py", line 77
    return os.access(f'/proc/{old_pid}/stat', os.F_OK)
                                           ^
SyntaxError: invalid syntax]: [This error is about the syntax error in code for Python2.]

Issue: The code contains f-string which is possible to define since Python3.6, but this code is interepreted by Python2.
Resolution: Do not use f-string in the code supposed to be Python2 compatible. instead `str.format` function.