[LyX/master] Catch improbable exception

[Jean-Marc Lasgouttes]

commit 5e33e4fc2c02f92dec8918ade9d1e191d1d697b3
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Sat Jul 13 00:24:21 2019 +0200

    Catch improbable exception
    
    We know that the exception is correct, but coverity does not.
    It would be much better to check that at compile time...
---
 src/support/os.cpp |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/support/os.cpp b/src/support/os.cpp
index c381203..ab9d415 100644
--- a/src/support/os.cpp
+++ b/src/support/os.cpp
@@ -49,7 +49,6 @@ int timeout_min()
 static string const python23_call(string const & binary, bool verbose = false)
 {
        const string version_info = " -c 'from __future__ import 
print_function;import sys; print(sys.version_info[:2], end=\"\")'";
-       static regex const python_reg("\\((\\d*), (\\d*)\\)");
        // Default to "python" if no binary is given.
        if (binary.empty())
                return "python -tt";
@@ -60,8 +59,14 @@ static string const python23_call(string const & binary, 
bool verbose = false)
        cmd_ret const out = runCommand(binary + version_info);
 
        smatch sm;
-       if (out.first < 0 || !regex_match(out.second, sm, python_reg))
+       try {
+               static regex const python_reg("\\((\\d*), (\\d*)\\)");
+               if (out.first < 0 || !regex_match(out.second, sm, python_reg))
+                       return string();
+       } catch(regex_error const & /*e*/) {
+               LYXERR0("Regex error! This should not happen.");
                return string();
+       }
 
        int major = convert<int>(sm.str(1));
        int minor = convert<int>(sm.str(2));