Use humanize for fuzzy time differences

It seems to do a bit better than ago (e.g. 4 months vs 146 days), and
looks like it’s maintained more often.

app/__init__.py

@@ -5,7 +5,7 @@ from datetime import datetime, timedelta, timezone
 from functools import partial
 from time import monotonic
 
-import ago
+import humanize
 import jinja2
 from flask import (
     Markup,
@@ -348,28 +348,17 @@ def format_delta(date):
         return "just now"
     if delta < timedelta(seconds=60):
         return "in the last minute"
-    return ago.human(
-        delta,
-        future_tense='{} from now',  # No-one should ever see this
-        past_tense='{} ago',
-        precision=1
-    )
+    return humanize.naturaltime(delta)
 
 
 def format_delta_days(date):
     now = datetime.now(timezone.utc)
     date = utc_string_to_aware_gmt_datetime(date)
-    delta = now - date
     if date.strftime('%Y-%M-%D') == now.strftime('%Y-%M-%D'):
         return "today"
     if date.strftime('%Y-%M-%D') == (now - timedelta(days=1)).strftime('%Y-%M-%D'):
         return "yesterday"
-    return ago.human(
-        delta,
-        precision=1,
-        future_tense='{} from now',
-        past_tense='{} ago',
-    )
+    return humanize.naturaltime(now - date)
 
 
 def valid_phone_number(phone_number):

requirements-app.txt

@@ -2,6 +2,7 @@
 # with package version changes made in requirements-app.txt
 
 ago==0.0.93
+humanize==1.0.0
 Flask==1.1.1
 Flask-WTF==0.14.3
 Flask-Login==0.4.1

requirements.txt

@@ -4,6 +4,7 @@
 # with package version changes made in requirements-app.txt
 
 ago==0.0.93
+humanize==1.0.0
 Flask==1.1.1
 Flask-WTF==0.14.3
 Flask-Login==0.4.1
@@ -29,10 +30,10 @@ git+https://github.com/alphagov/notifications-utils.git@36.6.0#egg=notifications
 git+https://github.com/alphagov/govuk-frontend-jinja.git@v0.5.1-alpha#egg=govuk-frontend-jinja==0.5.1-alpha
 
 ## The following requirements were added by pip freeze:
-awscli==1.17.15
+awscli==1.18.2
 bleach==3.1.0
 boto3==1.10.38
-botocore==1.14.15
+botocore==1.15.2
 certifi==2019.11.28
 chardet==3.0.4
 Click==7.0

tests/app/main/views/test_dashboard.py

@@ -262,9 +262,9 @@ def test_inbound_messages_shows_count_of_messages_when_there_are_no_messages(
 
 
 @pytest.mark.parametrize('index, expected_row', enumerate([
-    '07900 900000 message-1 1 hour ago',
-    '07900 900000 message-2 1 hour ago',
-    '07900 900000 message-3 1 hour ago',
+    '07900 900000 message-1 an hour ago',
+    '07900 900000 message-2 an hour ago',
+    '07900 900000 message-3 an hour ago',
     '07900 900002 message-4 3 hours ago',
     '07900 900004 message-5 5 hours ago',
     '07900 900006 message-6 7 hours ago',
@@ -558,7 +558,7 @@ def test_returned_letters_shows_count_of_recently_returned_letters(
         '0 returned letters latest report 8 days ago'
     )),
     ('2019-09-09', (
-        '0 returned letters latest report 146 days ago'
+        '0 returned letters latest report 4 months ago'
     )),
     ('2010-10-10', (
         '0 returned letters latest report 9 years ago'