Refactoring: Path API compatibility with pathlib

Refactored dupeGuru to make hscommon.path's API a bit close to pathlib's
API. It's not 100% compatible yet, but it's much better than before.

This is more of a hscommon refactoring than a dupeguru one, but since
duepGuru is the main user of Path, it was the driver behind the
refactoring.

This refactoring also see the introduction of @pathify, which ensure
Path arguments. Previously, we were often unsure of whether the caller
of a function was passing a Path or a str. This problem is now solved
and this allows us to remove hscommon.io, an ill-conceived attempt to
solve that same ambiguity problem.

Fixes #235.

hscommon/tests/util_test.py

@@ -11,7 +11,6 @@ from io import StringIO
 from pytest import raises
 
 from ..testutil import eq_
-from .. import io
 from ..path import Path
 from ..util import *
 
@@ -210,39 +209,49 @@ class TestCase_modified_after:
         monkeyplus.patch_osstat('first', st_mtime=42)
         assert modified_after('first', 'does_not_exist') # no crash
     
+    def test_first_file_is_none(self, monkeyplus):
+        # when the first file is None, we return False
+        monkeyplus.patch_osstat('second', st_mtime=42)
+        assert not modified_after(None, 'second') # no crash
+    
+    def test_second_file_is_none(self, monkeyplus):
+        # when the second file is None, we return True
+        monkeyplus.patch_osstat('first', st_mtime=42)
+        assert modified_after('first', None) # no crash
+    
 
 class TestCase_delete_if_empty:
     def test_is_empty(self, tmpdir):
         testpath = Path(str(tmpdir))
         assert delete_if_empty(testpath)
-        assert not io.exists(testpath)
+        assert not testpath.exists()
     
     def test_not_empty(self, tmpdir):
         testpath = Path(str(tmpdir))
-        io.mkdir(testpath + 'foo')
+        testpath['foo'].mkdir()
         assert not delete_if_empty(testpath)
-        assert io.exists(testpath)
+        assert testpath.exists()
     
     def test_with_files_to_delete(self, tmpdir):
         testpath = Path(str(tmpdir))
-        io.open(testpath + 'foo', 'w')
-        io.open(testpath + 'bar', 'w')
+        testpath['foo'].open('w')
+        testpath['bar'].open('w')
         assert delete_if_empty(testpath, ['foo', 'bar'])
-        assert not io.exists(testpath)
+        assert not testpath.exists()
     
     def test_directory_in_files_to_delete(self, tmpdir):
         testpath = Path(str(tmpdir))
-        io.mkdir(testpath + 'foo')
+        testpath['foo'].mkdir()
         assert not delete_if_empty(testpath, ['foo'])
-        assert io.exists(testpath)
+        assert testpath.exists()
     
     def test_delete_files_to_delete_only_if_dir_is_empty(self, tmpdir):
         testpath = Path(str(tmpdir))
-        io.open(testpath + 'foo', 'w')
-        io.open(testpath + 'bar', 'w')
+        testpath['foo'].open('w')
+        testpath['bar'].open('w')
         assert not delete_if_empty(testpath, ['foo'])
-        assert io.exists(testpath)
-        assert io.exists(testpath + 'foo')
+        assert testpath.exists()
+        assert testpath['foo'].exists()
     
     def test_doesnt_exist(self):
         # When the 'path' doesn't exist, just do nothing.
@@ -251,7 +260,7 @@ class TestCase_delete_if_empty:
     def test_is_file(self, tmpdir):
         # When 'path' is a file, do nothing.
         p = Path(str(tmpdir)) + 'filename'
-        io.open(p, 'w').close()
+        p.open('w').close()
         delete_if_empty(p) # no crash
     
     def test_ioerror(self, tmpdir, monkeypatch):
@@ -259,7 +268,7 @@ class TestCase_delete_if_empty:
         def do_raise(*args, **kw):
             raise OSError()
         
-        monkeypatch.setattr(io, 'rmdir', do_raise)
+        monkeypatch.setattr(Path, 'rmdir', do_raise)
         delete_if_empty(Path(str(tmpdir))) # no crash