Skip tests that're incompatible with pyicu

Some tests fail to run if PyICU is installed (it seems to break
compatibility across a few test dependencies, nothing we use outside of
tests directly).

Author: Hugo Osvaldo Barrera

.travis.yml

@@ -36,6 +36,10 @@ matrix:
       python: 3.6
       after_install:
         - echo click_repl >> requirements.txt
+    - # Run tests with incompatible test dependencies:
+      python: 3.6
+      after_install:
+        - echo pyicu >> requirements.txt
 
 addons:
   apt:

tests/helpers.py

@@ -0,0 +1,20 @@
+__all__ = [
+    'pyicu_sensitive',
+]
+
+import pytest
+
+
+def is_pyicu_installed():
+    try:
+        import icu  # noqa: F401: This is an import to tests if it's installed.
+    except ImportError:
+        return False
+    else:
+        return True
+
+
+pyicu_sensitive = pytest.mark.skipif(
+    is_pyicu_installed(),
+    reason="This test cannot be run with pyicu installed.",
+)

tests/test_cli.py

@@ -11,6 +11,7 @@
 from freezegun import freeze_time
 from hypothesis import given
 
+from tests.helpers import pyicu_sensitive
 from todoman.cli import cli, exceptions
 from todoman.model import Database, Todo
 
@@ -209,6 +210,7 @@ def test_move(tmpdir, runner, create):
     assert 'other_list' in result.output
 
 
+@pyicu_sensitive
 @freeze_time('2017-03-17 20:22:19')
 def test_dtstamp(tmpdir, runner, create):
     """Test that we add the DTSTAMP to new entries as per RFC5545."""
@@ -263,6 +265,7 @@ def test_default_due(
         )
 
 
+@pyicu_sensitive
 @freeze_time(datetime.datetime.now())
 def test_default_due2(tmpdir, runner, create, todos):
     cfg = tmpdir.join('config')
@@ -644,6 +647,7 @@ def test_todo_edit(runner, default_database, todo_factory):
     assert 'YARR!' in result.output
 
 
+@pyicu_sensitive
 @freeze_time('2017, 3, 20')
 def test_list_startable(tmpdir, runner, todo_factory):
     todo_factory(summary='started', start=datetime.datetime(2017, 3, 15))

tests/test_formatter.py

@@ -4,10 +4,12 @@
 import pytz
 from freezegun import freeze_time
 
+from tests.helpers import pyicu_sensitive
 from todoman.cli import cli
 from todoman.formatters import rgb_to_ansi
 
 
+@pyicu_sensitive
 @pytest.mark.parametrize('interval', [
     (65, 'in a minute'),
     (-10800, '3 hours ago'),