[LyX/master] Expose python 3 support to some testing

[Georg Baum]

commit 10b4a4718539ea45d908dc3d051ae2284f9678e6
Author: Georg Baum <b...@lyx.org>
Date:   Thu Jun 16 20:22:40 2016 +0200

    Expose python 3 support to some testing
    
    LyX will now always use the default python interpreter. This will hopefully
    help us sto see if one of them fails in some cases.

diff --git a/src/support/os.cpp b/src/support/os.cpp
index b1537e3..8afb96c 100644
--- a/src/support/os.cpp
+++ b/src/support/os.cpp
@@ -38,14 +38,16 @@ namespace lyx {
 namespace support {
 namespace os {
 
-static string const python2(string const & binary, bool verbose = false)
+static string const python23(string const & binary, bool verbose = false)
 {
        if (verbose)
                lyxerr << "Examining " << binary << "\n";
 
-       // Check whether this is a python 2 binary.
+       // Check whether this is a python 2 or 3 binary.
        cmd_ret const out = runCommand(binary + " -V 2>&1");
-       if (out.first < 0 || !prefixIs(out.second, "Python 2"))
+       if (out.first < 0 ||
+           (!prefixIs(out.second, "Python 2") &&
+            !prefixIs(out.second, "Python 3")))
                return string();
 
        if (verbose)
@@ -64,9 +66,9 @@ string const python(bool reset)
 {
        // FIXME THREAD
        // Check whether the first python in PATH is the right one.
-       static string command = python2("python -tt");
+       static string command = python23("python -tt");
        if (reset) {
-               command = python2("python -tt");
+               command = python23("python -tt");
        }
 
        if (command.empty()) {
@@ -85,13 +87,13 @@ string const python(bool reset)
                        for (int i = 0; i < list.size() && command.empty(); 
++i) {
                                string const binary = addName(localdir,
                                        list.at(i).toLocal8Bit().constData());
-                               command = python2(binary, true);
+                               command = python23(binary, true);
                        }
                }
 
                // Default to "python" if no usable binary was found.
                if (command.empty()) {
-                       lyxerr << "Warning: No python v2.x binary found.\n";
+                       lyxerr << "Warning: No python v2.x or 3.x binary 
found.\n";
                        command = "python";
                }