remove python 3.6 dep...

Pipfile

@@ -20,6 +20,3 @@ flask-assets = "*"
 
 [dev-packages]
 
-[requires]
-python_version = "3.6"
-

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "d3c62d103d9d8abe7d377f479d01885e9f5719a8826c284bc5931503071b7028"
+            "sha256": "2de5ec90d8ee6f01b6383c466d82f6361f2326579862ae1b3c4014efd9e52fc8"
         },
         "host-environment-markers": {
             "implementation_name": "cpython",
@@ -17,9 +17,7 @@
             "sys_platform": "linux"
         },
         "pipfile-spec": 6,
-        "requires": {
-            "python_version": "3.6"
-        },
+        "requires": {},
         "sources": [
             {
                 "name": "pypi",

app.py

@@ -46,14 +46,16 @@ def photo_resize_url(photo, size):
     if app.debug:
         return photo_set.url(photo.filename)
 
-    return f"{photo_set.config.base_url}img{size}/{photo.filename}"
+    return "{}img{}/{}".format(photo_set.config.base_url,
+                               size,
+                               photo.filename)
 
 
 def image_resize_url(image, size):
     if app.debug:
-        return f'static/images/{image}'
+        return 'static/images/{}'.format(image)
 
-    return f"/static/images/img{size}/{image}"
+    return "/static/images/img{}/{}".format(size, image)
 
 
 app.jinja_env.globals['photo_resize_url'] = photo_resize_url