Return user's gravatar if has no photo set

If the user has no photo set use her gravatar image if available
otherwise use the default avatar image defined in
`settings.DEFAULT_AVATAR_URL`

settings/common.py

@@ -305,3 +305,5 @@ if "test" in sys.argv:
     print ("\033[1;91mNo django tests.\033[0m")
     print ("Try: \033[1;33mpy.test\033[0m")
     sys.exit(0)
+
+DEFAULT_AVATAR_URL = ""

taiga/users/gravatar.py

@@ -0,0 +1,26 @@
+import hashlib
+from urllib.parse import urlencode
+
+from django.conf import settings
+
+GRAVATAR_BASE_URL = "http://www.gravatar.com/avatar/{}?{}"
+
+
+def get_gravatar_url(email: str, **options) -> str:
+    """Get the gravatar url associated to an email.
+
+    :param options: Additional options to gravatar:
+    - `d` defines what image url to show if no gravatar exists
+    - `s` defines the size of the avatar.
+    By default these options are:
+    - `d` is `settings.DEFAULT_AVATAR_URL`
+    - `s` gravatar's default value which is 80x80 px
+
+    :return: Gravatar url.
+    """
+    defaults = {'d': settings.DEFAULT_AVATAR_URL}
+    defaults.update(options)
+    email_hash = hashlib.md5(email.lower().encode()).hexdigest()
+    url = GRAVATAR_BASE_URL.format(email_hash, urlencode(defaults))
+
+    return url

taiga/users/serializers.py

@@ -18,12 +18,13 @@ from django.utils.translation import ugettext_lazy as _
 
 from rest_framework import serializers
 
-from taiga.projects.models import Project
-from .models import User, Role
+from .models import User
+from .gravatar import get_gravatar_url
 
 
 class UserSerializer(serializers.ModelSerializer):
     full_name_display = serializers.SerializerMethodField("get_full_name_display")
+    photo = serializers.SerializerMethodField("get_photo")
 
     class Meta:
         model = User
@@ -34,6 +35,10 @@ class UserSerializer(serializers.ModelSerializer):
     def get_full_name_display(self, obj):
         return obj.get_full_name() if obj else ""
 
+    def get_photo(self, user):
+        "Return the user photo or her gravatar"
+        return user.photo or get_gravatar_url(user.email)
+
 
 class RecoverySerializer(serializers.Serializer):
     token = serializers.CharField(max_length=200)

tests/unit/test_gravatar.py

@@ -0,0 +1,13 @@
+import hashlib
+
+from taiga.users.gravatar import get_gravatar_url
+
+
+def test_get_gravatar_url():
+    email = "user@email.com"
+    email_hash = hashlib.md5(email.encode()).hexdigest()
+    url = get_gravatar_url(email, s=40, d="default-image-url")
+
+    assert email_hash in url
+    assert 's=40' in url
+    assert 'd=default-image-url' in url