[gentoo-python] [PATCH] Support overriding PYTHON_COMPAT.

["Michał Górny" <mgorny@gentoo.org>]

PYTHON_COMPAT_OVERRIDE is an environment variable which overrides
the current value of PYTHON_COMPAT.

Useful for testing packages with new Python implementations quickly
without modifying the ebuild. Outputs a lot of noisy warnings to make
sure people notice how hacky it is.

Example use:

$ PYTHON_COMPAT_OVERRIDE=python3_3 emerge -1v dev-python/nose
---
 gx86/eclass/python-any-r1.eclass    | 5 ++++-
 gx86/eclass/python-r1.eclass        | 5 ++++-
 gx86/eclass/python-single-r1.eclass | 5 ++++-
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/gx86/eclass/python-any-r1.eclass b/gx86/eclass/python-any-r1.eclass
index ad56dc7..cd23aa4 100644
--- a/gx86/eclass/python-any-r1.eclass
+++ b/gx86/eclass/python-any-r1.eclass
@@ -65,7 +65,10 @@ if [[ ! ${_PYTHON_ANY_R1} ]]; then
 # @CODE
 # PYTHON_COMPAT=( python{2_5,2_6,2_7} )
 # @CODE
-if ! declare -p PYTHON_COMPAT &>/dev/null; then
+if [[ ${PYTHON_COMPAT_OVERRIDE} ]]; then
+	ewarn "PYTHON_COMPAT overriden: ${PYTHON_COMPAT_OVERRIDE}"
+	PYTHON_COMPAT=( ${PYTHON_COMPAT_OVERRIDE} )
+elif ! declare -p PYTHON_COMPAT &>/dev/null; then
 	die 'PYTHON_COMPAT not declared.'
 fi
 
diff --git a/gx86/eclass/python-r1.eclass b/gx86/eclass/python-r1.eclass
index 39de7f2..63bfb4e 100644
--- a/gx86/eclass/python-r1.eclass
+++ b/gx86/eclass/python-r1.eclass
@@ -66,7 +66,10 @@ inherit python-utils-r1
 # @CODE
 # PYTHON_COMPAT=( python{2_5,2_6,2_7} )
 # @CODE
-if ! declare -p PYTHON_COMPAT &>/dev/null; then
+if [[ ${PYTHON_COMPAT_OVERRIDE} ]]; then
+	ewarn "PYTHON_COMPAT overriden: ${PYTHON_COMPAT_OVERRIDE}"
+	PYTHON_COMPAT=( ${PYTHON_COMPAT_OVERRIDE} )
+elif ! declare -p PYTHON_COMPAT &>/dev/null; then
 	if [[ ${CATEGORY}/${PN} == dev-python/python-exec ]]; then
 		PYTHON_COMPAT=( "${_PYTHON_ALL_IMPLS[@]}" )
 	else
diff --git a/gx86/eclass/python-single-r1.eclass b/gx86/eclass/python-single-r1.eclass
index 51807f2..73f05f6 100644
--- a/gx86/eclass/python-single-r1.eclass
+++ b/gx86/eclass/python-single-r1.eclass
@@ -70,7 +70,10 @@ if [[ ! ${_PYTHON_SINGLE_R1} ]]; then
 # @CODE
 # PYTHON_COMPAT=( python{2_5,2_6,2_7} )
 # @CODE
-if ! declare -p PYTHON_COMPAT &>/dev/null; then
+if [[ ${PYTHON_COMPAT_OVERRIDE} ]]; then
+	ewarn "PYTHON_COMPAT overriden: ${PYTHON_COMPAT_OVERRIDE}"
+	PYTHON_COMPAT=( ${PYTHON_COMPAT_OVERRIDE} )
+elif ! declare -p PYTHON_COMPAT &>/dev/null; then
 	die 'PYTHON_COMPAT not declared.'
 fi
 
-- 
1.8.0.2