[libcalamares] Python API for callbacks from processes

This is an experiment in Python API that will allow a callback
function in the Python module to be called for each output line.
It builds on the run-a-process extensions that are being built
simultaneously.

src/libcalamares/PythonJob.cpp

@@ -36,6 +36,11 @@ BOOST_PYTHON_FUNCTION_OVERLOADS( check_target_env_output_list_overloads,
                                  CalamaresPython::check_target_env_output,
                                  1,
                                  3 );
+BOOST_PYTHON_MEMBER_FUNCTION_OVERLOADS( target_env_output_overloads,
+                                        target_env_output,
+                                        2,
+                                        4 );
+
 BOOST_PYTHON_MODULE( libcalamares )
 {
     bp::object package = bp::scope();
@@ -56,7 +61,11 @@ BOOST_PYTHON_MODULE( libcalamares )
               &CalamaresPython::PythonJobInterface::setprogress,
               bp::args( "progress" ),
               "Reports the progress status of this job to Calamares, "
-              "as a real number between 0 and 1." );
+              "as a real number between 0 and 1." )
+        .def( "target_env_output",
+              &CalamaresPython::PythonJobInterface::target_env_output,
+              target_env_output_overloads( bp::args( "args", "callback", "stdin", "timeout" ), "docstring"))
+        ;
 
     bp::class_< CalamaresPython::GlobalStoragePythonWrapper >( "GlobalStorage",
                                                                bp::init< Calamares::GlobalStorage* >() )

src/libcalamares/PythonJobApi.cpp

@@ -171,6 +171,13 @@ PythonJobInterface::setprogress( qreal progress )
     }
 }
 
+int
+PythonJobInterface::target_env_output( const boost::python::list& args, const std::string& callback, const std::string& stdin, int timeout )
+{
+    cWarning()  << "target env" << _bp_list_to_qstringlist(args) << "cb" << callback.c_str() << "stdin" << stdin.c_str() << "timeout" << timeout;
+    return 0;
+}
+
 std::string
 obscure( const std::string& string )
 {

src/libcalamares/PythonJobApi.h

@@ -63,6 +63,12 @@ public:
     boost::python::dict configuration;
 
     void setprogress( qreal progress );
+    /** @brief Run the command @p args and process lines of output
+     *
+     * Calls the function @p callback from the job module on each
+     * line of output. Returns the exit code of the command.
+     */
+    int target_env_output( const boost::python::list& args, const std::string& callback, const std::string& stdin = std::string(), int timeout = 10 );
 
 private:
     Calamares::PythonJob* m_parent;