From 4c2c80dcdaf78ebdd44185762484f9db9ff147b8 Mon Sep 17 00:00:00 2001
From: Erik Rose <erik@mozilla.com>
Date: Fri, 12 Feb 2016 17:23:29 -0500
Subject: [PATCH] Fix DeterminePythonVersion().

Ported from #1751.

* Make sure any Python passed in as $LE_PYTHON actually exists.
* Dodge a word-splitting bug: `a='a b'; export a=${a:-c}; echo $a` gives `a` instead of `a b` under shells that respect POSIX.1, like dash.
---
 letsencrypt-auto-source/letsencrypt-auto        | 17 +++++++----------
 .../letsencrypt-auto.template                   | 17 +++++++----------
 2 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/letsencrypt-auto-source/letsencrypt-auto b/letsencrypt-auto-source/letsencrypt-auto
index ea3f7a4bb..bfb41e240 100755
--- a/letsencrypt-auto-source/letsencrypt-auto
+++ b/letsencrypt-auto-source/letsencrypt-auto
@@ -91,18 +91,15 @@ ExperimentalBootstrap() {
 }
 
 DeterminePythonVersion() {
-  if command -v python2.7 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python2.7}
-  elif command -v python27 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python27}
-  elif command -v python2 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python2}
-  elif command -v python > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python}
-  else
-    echo "Cannot find any Pythons... please install one!"
+  for LE_PYTHON in "$LE_PYTHON" python2.7 python27 python2 python; do
+    # Break (while keeping the LE_PYTHON value) if found.
+    command -v "$LE_PYTHON" > /dev/null && break
+  done
+  if [ "$?" != "0" ]; then
+    echo "Cannot find any Pythons; please install one!"
     exit 1
   fi
+  export LE_PYTHON
 
   PYVER=`"$LE_PYTHON" -V 2>&1 | cut -d" " -f 2 | cut -d. -f1,2 | sed 's/\.//'`
   if [ $PYVER -lt 26 ]; then
diff --git a/letsencrypt-auto-source/letsencrypt-auto.template b/letsencrypt-auto-source/letsencrypt-auto.template
index b65b55163..2572e13d6 100755
--- a/letsencrypt-auto-source/letsencrypt-auto.template
+++ b/letsencrypt-auto-source/letsencrypt-auto.template
@@ -91,18 +91,15 @@ ExperimentalBootstrap() {
 }
 
 DeterminePythonVersion() {
-  if command -v python2.7 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python2.7}
-  elif command -v python27 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python27}
-  elif command -v python2 > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python2}
-  elif command -v python > /dev/null ; then
-    export LE_PYTHON=${LE_PYTHON:-python}
-  else
-    echo "Cannot find any Pythons... please install one!"
+  for LE_PYTHON in "$LE_PYTHON" python2.7 python27 python2 python; do
+    # Break (while keeping the LE_PYTHON value) if found.
+    command -v "$LE_PYTHON" > /dev/null && break
+  done
+  if [ "$?" != "0" ]; then
+    echo "Cannot find any Pythons; please install one!"
     exit 1
   fi
+  export LE_PYTHON
 
   PYVER=`"$LE_PYTHON" -V 2>&1 | cut -d" " -f 2 | cut -d. -f1,2 | sed 's/\.//'`
   if [ $PYVER -lt 26 ]; then