Merge pull request #6042 from johnhaddon/pythonNoUserSite

Wrapper : Set `PYTHONNOUSERSITE=1`

Changes.md

@@ -57,6 +57,7 @@ Fixes
 - usdview : Added Windows support (#5599).
 - ContextTracker : Removed unnecessary reference increment/decrement from `isTracked()`, `context()` and `isEnabled()`.
 - Menu : Fixed bug causing a menu item's tooltip to not hide when moving the cursor to another menu item without a tooltip.
+- Python : Fixed startup failures caused by conflicting Python modules in the user `site-packages` directory.
 
 API
 ---
@@ -117,6 +118,7 @@ Breaking Changes
 - FreezeTransform : Constant primitive variables with point/vector interpretations are now also transformed (this is more correct, but it is a change in behaviour).
 - ImageGadget : Remove non-const variant of `getContext()`.
 - LazyMethod : `deferUntilPlaybackStops` now requires that the Widget has a `scriptNode()` method rather than a `context()` method.
+- Python : Gaffer now disables the user site-packages directory by setting `PYTHONNOUSERSITE=1`. To revert to the previous behaviour, set `PYTHONNOUSERSITE=0` before launching Gaffer.
 
 Build
 -----

bin/gaffer

@@ -170,6 +170,15 @@ fi
 
 prependToPath "$GAFFER_ROOT/python" PYTHONPATH
 
+if [[ -z $PYTHONNOUSERSITE ]] ; then
+	# Prevent Python automatically adding a user-level `site-packages`
+	# directory to the `sys.path`. These frequently contain modules which
+	# conflict with our own. Users who know what they are doing can set
+	# `PYTHONNOUSERSITE=0` before running Gaffer if they want to use
+	# the user directory.
+	export PYTHONNOUSERSITE=1
+fi
+
 # Stop Cortex from making all Python modules load with RTLD_GLOBAL.
 export IECORE_RTLD_GLOBAL=0
 

bin/gaffer.cmd

@@ -48,6 +48,15 @@ set PYTHONHOME=%GAFFER_ROOT%
 
 call :prependToPath "%GAFFER_ROOT%\python" PYTHONPATH
 
+if "%PYTHONNOUSERSITE%" EQU "" (
+	REM Prevent Python automatically adding a user-level `site-packages`
+	REM directory to the `sys.path`. These frequently contain modules which
+	REM conflict with our own. Users who know what they are doing can set
+	REM `PYTHONNOUSERSITE=0` before running Gaffer if they want to use
+	REM the user directory.
+	set PYTHONNOUSERSITE=1
+)
+
 call :prependToPath "%GAFFER_ROOT%\lib" PATH
 
 set QT_OPENGL=desktop