remove py2 remnants and use mocks in tests

fstring wip
Run pyupgrade
fix broken pyupgrade fstring
run pyupgrade on plugin dir
fixup! remove py2 remnants and use mocks in tests
small print bugfix
The file=sys.stderr was part of the format(), so an error got printed to
stdout
Drop use of codecs package
Use builtins.open() instead
fixup! remove py2 remnants and use mocks in tests

jrnl/Entry.py

@@ -1,7 +1,5 @@
 #!/usr/bin/env python
-# encoding: utf-8
 
-from __future__ import unicode_literals
 import re
 import textwrap
 from datetime import datetime
@@ -51,14 +49,14 @@ class Entry:
 
     @staticmethod
     def tag_regex(tagsymbols):
-        pattern = r'(?u)(?:^|\s)([{tags}][-+*#/\w]+)'.format(tags=tagsymbols)
-        return re.compile(pattern, re.UNICODE)
+        pattern = fr'(?u)(?:^|\s)([{tagsymbols}][-+*#/\w]+)'
+        return re.compile(pattern)
 
     def _parse_tags(self):
         tagsymbols = self.journal.config['tagsymbols']
-        return set(tag.lower() for tag in re.findall(Entry.tag_regex(tagsymbols), self.text))
+        return {tag.lower() for tag in re.findall(Entry.tag_regex(tagsymbols), self.text)}
 
-    def __unicode__(self):
+    def __str__(self):
         """Returns a string representation of the entry to be written into a journal file."""
         date_str = self.date.strftime(self.journal.config['timeformat'])
         title = "[{}] {}".format(date_str, self.title.rstrip("\n "))
@@ -106,7 +104,7 @@ class Entry:
             )
 
     def __repr__(self):
-        return "<Entry '{0}' on {1}>".format(self.title.strip(), self.date.strftime("%Y-%m-%d %H:%M"))
+        return "<Entry '{}' on {}>".format(self.title.strip(), self.date.strftime("%Y-%m-%d %H:%M"))
 
     def __hash__(self):
         return hash(self.__repr__())