Improve TimeZoneFix with dunder methods

Makefile

@@ -1,7 +1,7 @@
 test: lint vermin pytest
 
 lint:
-	flake8 --exclude=".env,.git,docs" --ignore=E501,W504 .
+	flake8 --exclude=".env,.git,docs" --ignore=E501,W504 aerofiles tests
 
 vermin:
 	vermin aerofiles

aerofiles/util/__init__.py

@@ -0,0 +1,3 @@
+# flake8: noqa
+
+from .timezone import TimeZoneFix

aerofiles/util/timezone.py

@@ -2,10 +2,33 @@
 
 
 class TimeZoneFix(datetime.tzinfo):
+    """
+    A simple implementation of tzinfo to store timezone of IGC fixes.
 
-    def __init__(self, fix):
+    An alternative would be, to use "timezone" which is part of
+    Python since v3.2. However, because we try to be python 2.6+
+    compatible, we use this implementation. It can be replaced,
+    if we set Python 3.x as a minimum requirement for aerofiles.
+    """
+
+    def __init__(self, fix=0):
         self.fix = fix
 
+    def __eq__(self, other):
+        if isinstance(other, TimeZoneFix):
+            return self.fix == other.fix
+        return NotImplemented
+
+    def __hash__(self):
+        return hash(self.fix)
+
+    def __repr__(self):
+        """Convert to formal string, for repr().
+        """
+        return "%s.%s(%r)" % (self.__class__.__module__,
+                              self.__class__.__qualname__,
+                              self.fix)
+
     def utcoffset(self, dt):
         return datetime.timedelta(hours=self.fix)
 

tests/igc/test_timezone.py

@@ -0,0 +1,21 @@
+import copy
+
+from aerofiles.util import TimeZoneFix
+
+
+def test_not_equal():
+    tz1 = TimeZoneFix(1)
+    tz2 = TimeZoneFix(2)
+    assert (tz1 != tz2)
+
+
+def test_equal():
+    tz1 = TimeZoneFix(1)
+    tz2 = TimeZoneFix(1)
+    assert (tz1 == tz2)
+
+
+def test_deepcopy():
+    tz1 = TimeZoneFix(1)
+    tz2 = copy.deepcopy(tz1)
+    assert (tz1 == tz2)