[WIP] Pipe nickname and password into Java prompt

This currently fails with "Error: Could not get account information. Is STDIN connected?" for all three versions due to the usage of prompt() in briar-headless.

CC @grote

src/ui/setup.py

@@ -17,6 +17,7 @@
 
 from gi.repository import Gtk
 from .gi_composites import GtkTemplate
+from subprocess import Popen, PIPE
 
 
 @GtkTemplate(ui='/app/briar/gtk/ui/setup.ui')
@@ -41,3 +42,22 @@ class BriarSetupWindow(Gtk.ApplicationWindow):
 
     def on_password_button_clicked(self, button):
         self.password = self.password_entry.get_text()
+        self.start_briar_headless()
+
+    def start_briar_headless(self):
+        p = Popen(['java', '-jar', '/app/briar/briar-headless.jar', '-v'], stdin=PIPE, universal_newlines=True)
+        p.communicate(self.username + '\n' + self.password + '\n')
+
+    def start_briar_headless_v2(self):
+        with Popen(['java', '-jar', '/app/briar/briar-headless.jar', '-v'], stdin=PIPE) as p:
+            p.stdin.write(bytes(self.username + '\n', 'utf-8'))
+            p.stdin.write(bytes(self.password + '\n', 'utf-8'))
+            p.stdin.close()
+            p.wait()
+
+    def start_briar_headless_v3(self):
+        print(self.username + '\n' + self.password + '\n')
+        p = run(['java', '-jar', '/app/briar/briar-headless.jar', '-v'], stdout=PIPE,
+                input=self.username + '\n' + self.password + '\n', encoding='ascii')
+        print(p.returncode)
+