Fix healthcheck in python3

Subprocess returns stdout as bytes instead of str nowadays, so I
addressed it in a quick and dirty way.

The extra return in healthcheck function is added there to stop the app
from complaining about it and also because I discovered that the
solution for tracking printer status here is essentially hardcoded for
English, while my local test environment outputs lpstat logs
in Ukrainian.

render.py

@@ -7,6 +7,7 @@ import time
 
 import cairocffi as cairo
 import flask
+from flask import json
 import pangocffi as pango
 import pangocairocffi as pangocairo
 
@@ -59,8 +60,7 @@ class Renderer(object):
             layout.apply_markup('<span font_desc="%s">%s</span>' % (fontname, text))
         else:
             font = pango.FontDescription()
-            font.family = "Sans"
-            font.size = 65
+            font.family = fontname
             layout.font_description = font
             layout.text = text
 
@@ -81,10 +81,10 @@ def healthcheck():
     last_checked, last_status, last_details = app.health
     if time.time() - last_checked < 1:
         return last_status, last_details
-    output = subprocess.check_output(['lpstat', '-p', '-d'])
+    output = subprocess.run(['lpstat', '-p', '-d'], capture_output=True).stdout
     mark = False
-    for line in output.split('\n'):
-        line = line.strip()
+    for line in output.split(b'\n'):
+        line = line.strip().decode('utf-8')
         if line.startswith('printer DYMO_LabelWriter_450'):
             if 'is idle.' in line:
                 return True, 'Idle'
@@ -98,13 +98,13 @@ def healthcheck():
                 app.health = (time.time(), False, line)
                 return False, line
         mark = False
+    return False, 'Printer is down or there\'s something wrong with lpstat output.'
 
-# TODO: Uncomment and fix this
 
-# @app.route('/health')
-# def health():
-#     ok, details = healthcheck()
-#     return json.dumps({'ok': ok, 'details': details})
+@app.route('/health')
+def health():
+    ok, details = healthcheck()
+    return json.dumps({'ok': ok, 'details': details})
 
 @app.route('/stuff/preview/<int:size>/')
 def stuff_preview(size):
@@ -124,7 +124,7 @@ def stuff_print(size):
     if not healthcheck()[0]:
         return 'Printer is down.'
     last = app.last
-    print(last, time.time() - last)
+    print((last, time.time() - last))
     if time.time() - last < DELAY:
         return 'Please wait {} more seconds before next print.'.format(int(DELAY - (time.time() - last)))
     text = flask.request.args.get('text')