diff --git a/pkgs/development/python-modules/datasette/default.nix b/pkgs/development/python-modules/datasette/default.nix
index 48de7e86b92e..828976f0e9fb 100644
--- a/pkgs/development/python-modules/datasette/default.nix
+++ b/pkgs/development/python-modules/datasette/default.nix
@@ -3,7 +3,6 @@
 , fetchFromGitHub
 , click
 , click-default-group
-, sanic
 , jinja2
 , hupper
 , pint
@@ -14,17 +13,20 @@
 , black
 , aiohttp
 , beautifulsoup4
+, uvicorn
+, asgiref
+, aiofiles
 }:
 
 buildPythonPackage rec {
   pname = "datasette";
-  version = "0.28";
+  version = "0.29.3";
 
   src = fetchFromGitHub {
     owner = "simonw";
     repo = "datasette";
     rev = version;
-    sha256 = "1m2s03gyq0ghjc3s0b5snpinisddywpgii2f0zqa3v4ljmzanx7h";
+    sha256 = "0cib7pd4z240ncck0pskzvizblhwkr42fsjpd719wdxy4scs7yqa";
   };
 
   buildInputs = [ pytestrunner ];
@@ -32,11 +34,12 @@ buildPythonPackage rec {
   propagatedBuildInputs = [
     click
     click-default-group
-    sanic
     jinja2
     hupper
     pint
     pluggy
+    uvicorn
+    aiofiles
   ];
 
   checkInputs = [
@@ -45,6 +48,7 @@ buildPythonPackage rec {
     aiohttp
     beautifulsoup4
     black
+    asgiref
   ];
 
   postConfigure = ''
@@ -52,8 +56,9 @@ buildPythonPackage rec {
       --replace "click-default-group==1.2" "click-default-group" \
       --replace "Sanic==0.7.0" "Sanic" \
       --replace "hupper==1.0" "hupper" \
-      --replace "pint==0.8.1" "pint" \
-      --replace "Jinja2==2.10.1" "Jinja2"
+      --replace "pint~=0.8.1" "pint" \
+      --replace "Jinja2==2.10.1" "Jinja2" \
+      --replace "uvicorn~=0.8.4" "uvicorn"
   '';
 
   # many tests require network access
diff --git a/pkgs/development/python-modules/sanic/default.nix b/pkgs/development/python-modules/sanic/default.nix
index 6aae4c11fdd4..5c1e0e812468 100644
--- a/pkgs/development/python-modules/sanic/default.nix
+++ b/pkgs/development/python-modules/sanic/default.nix
@@ -15,15 +15,76 @@
 , pytest-sanic
 , pytest-sugar
 , pytest-benchmark
+
+# required just httpcore / requests-async
+, h11
+, h2
+, certifi
+, chardet
+, idna
+, requests
+, rfc3986
+, uvicorn
 }:
 
+let
+
+  # This version of sanic depends on two packages that have been deprecated by
+  # their development teams:
+  #
+  # - requests-async [where first line of pypi says to use `http3` instead now]
+  # - httpcore       [where the homepage redirects to `http3` now]
+  #
+  # Since no other packages in nixpkg depend on these right now, define these
+  # packages just as local dependencies here, to avoid bloat.
+
+  httpcore = buildPythonPackage rec {
+    pname = "httpcore";
+    version = "0.3.0";
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "0n3bamaixxhcm27gf1ws3g6rkamvqx87087c88r6hyyl52si1ycn";
+    };
+
+    propagatedBuildInputs = [ certifi chardet h11 h2 idna rfc3986 ];
+
+    # relax pinned old version of h11
+    postConfigure = ''
+      substituteInPlace setup.py \
+        --replace "h11==0.8.*" "h11"
+      '';
+
+    # LICENCE.md gets propagated without this, causing collisions
+    postInstall = ''
+      rm $out/LICENSE.md
+    '';
+  };
+
+  requests-async = buildPythonPackage rec {
+    pname = "requests-async";
+    version = "0.5.0";
+    src = fetchPypi {
+      inherit pname version;
+      sha256 = "8731420451383196ecf2fd96082bfc8ae5103ada90aba185888499d7784dde6f";
+    };
+
+    propagatedBuildInputs = [ requests httpcore ];
+
+    # LICENCE.md gets propagated without this, causing collisions
+    postInstall = ''
+      rm $out/LICENSE.md
+    '';
+  };
+
+in
+
 buildPythonPackage rec {
   pname = "sanic";
-  version = "19.3.1";
+  version = "19.6.3";
 
   src = fetchPypi {
     inherit pname version;
-    sha256 = "ce434eb154872ca64493a6c3a288f11fd10bca0de7be7bf9f1d0d063185e51ec";
+    sha256 = "0b1qqsvdjkibrw5kgr0pm7n7jzb1403132wjmb0lx3k5wyvqfi95";
   };
 
   propagatedBuildInputs = [
@@ -31,6 +92,7 @@ buildPythonPackage rec {
     aiofiles
     websockets
     multidict
+    requests-async
     uvloop
     ujson
   ];
@@ -44,11 +106,20 @@ buildPythonPackage rec {
     pytest-sanic
     pytest-sugar
     pytest-benchmark
+    uvicorn
   ];
 
+  # Sanic says it needs websockets 7.x, but the changelog for 8.x is actually
+  # nearly compatible with sanic's use. So relax this constraint, with a small
+  # required code change.
   postConfigure = ''
-    substituteInPlace setup.py \
-      --replace "websockets>=6.0,<7.0" "websockets"
+    substituteInPlace setup.py --replace \
+      "websockets>=7.0,<8.0"             \
+      "websockets>=7.0,<9.0"
+    substituteInPlace sanic/websocket.py --replace    \
+           "self.websocket.subprotocol = subprotocol" \
+           "self.websocket.subprotocol = subprotocol
+            self.websocket.is_client = False"
   '';
 
   # 10/500 tests ignored due to missing directory and
diff --git a/pkgs/development/python-modules/uvicorn/default.nix b/pkgs/development/python-modules/uvicorn/default.nix
index 9f7efef1e843..a525846be767 100644
--- a/pkgs/development/python-modules/uvicorn/default.nix
+++ b/pkgs/development/python-modules/uvicorn/default.nix
@@ -43,6 +43,12 @@ buildPythonPackage rec {
     pytest
   '';
 
+  # LICENCE.md gets propagated without this, causing collisions
+  # see https://github.com/encode/uvicorn/issues/392
+  postInstall = ''
+    rm $out/LICENSE.md
+  '';
+
   meta = with lib; {
     homepage = https://www.uvicorn.org/;
     description = "The lightning-fast ASGI server";
diff --git a/pkgs/development/python-modules/websockets/default.nix b/pkgs/development/python-modules/websockets/default.nix
index 589a8089fcaa..9202d02ad5b9 100644
--- a/pkgs/development/python-modules/websockets/default.nix
+++ b/pkgs/development/python-modules/websockets/default.nix
@@ -3,6 +3,7 @@
 , buildPythonPackage
 , pythonOlder
 , pytest
+, stdenv
 }:
 
 buildPythonPackage rec {
@@ -18,6 +19,9 @@ buildPythonPackage rec {
 
   disabled = pythonOlder "3.3";
 
+  # Tests fail on Darwin with `OSError: AF_UNIX path too long`
+  doCheck = !stdenv.isDarwin;
+
   meta = with lib; {
     description = "WebSocket implementation in Python 3";
     homepage = "https://github.com/aaugustin/websockets";