Python: set DETERMINISTIC_BUILD and PYTHONHASHSEED in setupHook

The Python interpreters are patched so they can build .pyc bytecode free
of certain indeterminism.

When building Python packages we currently set

```
compiling python files.
in nix store.
DETERMINISTIC_BUILD=1;
PYTHONHASHSEED = 0;
```

Instead if setting these environment variables in the function that
builds the package, this commit sets the variables instead in the Python
setup hook. That way, whenever Python is included in a derivation, these
variables are set.

See also the issue https://github.com/NixOS/nixpkgs/issues/25707.

pkgs/development/interpreters/python/cpython/2.7/default.nix

@@ -15,6 +15,7 @@
 , expat
 , libffi
 , CF, configd, coreutils
+, python-setup-hook
 # For the Python package set
 , pkgs, packageOverrides ? (self: super: {})
 }:
@@ -150,7 +151,7 @@ in stdenv.mkDerivation {
     NIX_CFLAGS_COMPILE = optionalString stdenv.isDarwin "-msse2";
     DETERMINISTIC_BUILD = 1;
 
-    setupHook = ./setup-hook.sh;
+    setupHook = python-setup-hook sitePackages;
 
     postPatch = optionalString (x11Support && (tix != null)) ''
           substituteInPlace "Lib/lib-tk/Tix.py" --replace "os.environ.get('TIX_LIBRARY')" "os.environ.get('TIX_LIBRARY') or '${tix}/lib'"

pkgs/development/interpreters/python/cpython/2.7/setup-hook.sh

@@ -1,15 +0,0 @@
-addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python2.7/site-packages
-}
-
-toPythonPath() {
-    local paths="$1"
-    local result=
-    for i in $paths; do
-        p="$i/lib/python2.7/site-packages"
-        result="${result}${result:+:}$p"
-    done
-    echo $result
-}
-
-envHooks+=(addPythonPath)

pkgs/development/interpreters/python/cpython/3.3/default.nix

@@ -77,7 +77,7 @@ in stdenv.mkDerivation {
                         )
   '';
 
-  setupHook = ./setup-hook.sh;
+  setupHook = python-setup-hook sitePackages;
 
   postInstall = ''
     # needed for some packages, especially packages that backport functionality

pkgs/development/interpreters/python/cpython/3.3/setup-hook.sh

@@ -1,15 +0,0 @@
-addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python3.3/site-packages
-}
-
-toPythonPath() {
-    local paths="$1"
-    local result=
-    for i in $paths; do
-        p="$i/lib/python3.3/site-packages"
-        result="${result}${result:+:}$p"
-    done
-    echo $result
-}
-
-envHooks+=(addPythonPath)

pkgs/development/interpreters/python/cpython/3.4/default.nix

@@ -13,6 +13,7 @@
 , callPackage
 , self
 , CF, configd
+, python-setup-hook
 # For the Python package set
 , pkgs, packageOverrides ? (self: super: {})
 }:
@@ -100,7 +101,7 @@ in stdenv.mkDerivation {
      ''}
   '';
 
-  setupHook = ./setup-hook.sh;
+  setupHook = python-setup-hook sitePackages;
 
   postInstall = ''
     # needed for some packages, especially packages that backport functionality

pkgs/development/interpreters/python/cpython/3.4/setup-hook.sh

@@ -1,15 +0,0 @@
-addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python3.4/site-packages
-}
-
-toPythonPath() {
-    local paths="$1"
-    local result=
-    for i in $paths; do
-        p="$i/lib/python3.4/site-packages"
-        result="${result}${result:+:}$p"
-    done
-    echo $result
-}
-
-envHooks+=(addPythonPath)

pkgs/development/interpreters/python/cpython/3.5/default.nix

@@ -13,6 +13,7 @@
 , callPackage
 , self
 , CF, configd
+, python-setup-hook
 # For the Python package set
 , pkgs, packageOverrides ? (self: super: {})
 }:
@@ -102,7 +103,7 @@ in stdenv.mkDerivation {
      ''}
   '';
 
-  setupHook = ./setup-hook.sh;
+  setupHook = python-setup-hook sitePackages;
 
   postInstall = ''
     # needed for some packages, especially packages that backport functionality

pkgs/development/interpreters/python/cpython/3.5/setup-hook.sh

@@ -1,15 +0,0 @@
-addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python3.5/site-packages
-}
-
-toPythonPath() {
-    local paths="$1"
-    local result=
-    for i in $paths; do
-        p="$i/lib/python3.5/site-packages"
-        result="${result}${result:+:}$p"
-    done
-    echo $result
-}
-
-envHooks+=(addPythonPath)

pkgs/development/interpreters/python/cpython/3.6/default.nix

@@ -14,6 +14,7 @@
 , callPackage
 , self
 , CF, configd
+, python-setup-hook
 # For the Python package set
 , pkgs, packageOverrides ? (self: super: {})
 }:
@@ -94,7 +95,7 @@ in stdenv.mkDerivation {
      ''}
   '';
 
-  setupHook = ./setup-hook.sh;
+  setupHook = python-setup-hook sitePackages;
 
   postInstall = ''
     # needed for some packages, especially packages that backport functionality

pkgs/development/interpreters/python/cpython/3.6/setup-hook.sh

@@ -1,15 +0,0 @@
-addPythonPath() {
-    addToSearchPathWithCustomDelimiter : PYTHONPATH $1/lib/python3.6/site-packages
-}
-
-toPythonPath() {
-    local paths="$1"
-    local result=
-    for i in $paths; do
-        p="$i/lib/python3.6/site-packages"
-        result="${result}${result:+:}$p"
-    done
-    echo $result
-}
-
-envHooks+=(addPythonPath)