[entropy.spm] move Portage bashism to external script

Portage stores package environment variables inside it's environment
file that has to be sourced in order to correctly retrieve the
variable value

Makefile

@@ -38,7 +38,9 @@ entropy-install:
 	install -d -m 775 $(DESTDIR)/$(VARDIR)/log/entropy
 	touch $(DESTDIR)/$(VARDIR)/log/entropy/.keep
 
-	cp lib/entropy $(DESTDIR)/$(LIBDIR)/entropy/lib/ -Ra
+	chmod +x lib/entropy/spm/plugins/interfaces/portage_plugin/env_sourcer.sh
+	cp -Ra lib/entropy $(DESTDIR)/$(LIBDIR)/entropy/lib/
+
 	ln -sf lib $(DESTDIR)/$(LIBDIR)/entropy/libraries
 	install -m 755 misc/entropy.sh $(DESTDIR)$(PREFIX)/sbin/
 	install -m 755 services/repository_services $(DESTDIR)/etc/init.d/

lib/entropy/spm/plugins/interfaces/portage_plugin/__init__.py

@@ -972,30 +972,17 @@ class PortagePlugin(SpmPlugin):
             return defaults[0]
 
     def __source_env_get_var(self, env_file, env_var):
-        cmd = "/bin/bash -c \"source " + env_file + \
-            " && echo ${" + env_var + "}\""
-        tmp_fd, tmp_file = tempfile.mkstemp(prefix = "etp_portage")
-        try:
-            with os.fdopen(tmp_fd, "w") as std_f:
-                proc = subprocess.Popen(shlex.split(cmd), stdout = std_f,
-                    stderr = std_f)
-                sts = proc.wait()
-                std_f.flush()
-
-            enc = etpConst['conf_encoding']
-            with codecs.open(tmp_file, "r", encoding=enc) as std_f:
-                output = std_f.read()
-        finally:
-            try:
-                os.close(tmp_fd)
-            except OSError:
-                pass
-            os.remove(tmp_file)
-
+        current_mod = sys.modules[__name__].__file__
+        dirname = os.path.dirname(current_mod)
+        exec_path = os.path.join(dirname, "env_sourcer.sh")
+        args = [exec_path, env_file, env_var]
+        proc = subprocess.Popen(args, stdout = subprocess.PIPE)
+        sts = proc.wait()
         if sts != 0:
-            raise IOError("cannot source %s and get %s => %s" % (env_file,
-                env_var, repr(output)))
-        return output.strip()
+            raise IOError("cannot source %s and get %s" % (
+                    env_file, env_var,))
+        output = proc.stdout.read().strip()
+        return output
 
     def __pkg_sources_filtering(self, sources):
         sources.discard("->")

lib/entropy/spm/plugins/interfaces/portage_plugin/env_sourcer.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+# /bin/sh won't work
+
+. ${1} || exit 1
+eval echo \${${2}}