Fix dh_make call for Debian packaging

[pluehne]

dh_make recently changed from Python 2 to Python 3. For this reason, the call to dh_make with Python 2 won’t work on systems with new dh_make versions. Instead of locking the Python version to Python 2, call Python without the fixed version number. This should be safe, because we can expect Linux distributions to ship a version of dh_make that works with the system’s default Python version.

[larsxschneider]

What would happen if I have the wrong Python version? Would it scream loud or error silently?

[pluehne]

Calling dh_make with the wrong Python version results in errors.

dh_make 2.201701 (the new version) with Python 2 gives a module dependency error:

Traceback (most recent call last):
  File "/usr/bin/dh_make", line 16, in <module>
    from enum import Enum
ImportError: No module named enum

dh_make 2.201608 (the old version) with Python 3 even results in a syntax error:

  File "dh_make", line 715
    os.mkdir('source', 0755)
                          ^
SyntaxError: invalid token

So in both cases, we get an error.

[pluehne]

However, we should, perhaps, require dh_make to succeed for any of the later commands. In this way, make would get an error exit code and report the version mismatch more nicely.

Currently, the result would be a file not found error toward the end of the Makefile.

[pluehne]

By the way, I’d like to call dh_make without python and to rely on a proper shebang declaration. However, dh_make as of 2.201608 declares /usr/bin/python as its interpreter without specifying the required Python version explicitly. This is unfortunate, because now, we have to care about the correct version. However, dh_make 2.201701 has a proper interpreter directive (/usr/bin/python3).