[initcpiocfg] Polish PR #1290

- List discrete years in copyright
 - Add docstrings
 - Massage detect_plymouth() to return bool (easier in if() context)

src/modules/initcpiocfg/main.py

@@ -4,7 +4,7 @@
 # === This file is part of Calamares - <https://github.com/calamares> ===
 #
 #   Copyright 2014, Rohan Garg <rohan@kde.org>
-#   Copyright 2015 - 2019, Philip Müller <philm@manjaro.org>
+#   Copyright 2015,2019, Philip Müller <philm@manjaro.org>
 #   Copyright 2017, Alf Gaida <agaida@sidution.org>
 #   Copyright 2019, Adriaan de Groot <groot@kde.org>
 #
@@ -102,10 +102,16 @@ def write_mkinitcpio_lines(hooks, modules, files, root_mount_point):
         mkinitcpio_file.write("\n".join(mklins) + "\n")
 
 def detect_plymouth():
+    """
+    Checks existence (runnability) of plymouth in the target system.
+
+    @return True if plymouth exists in the target, False otherwise
+    """
+    # Used to only check existence of path /usr/bin/plymouth in target
     isPlymouth = target_env_call(["sh", "-c", "which plymouth"])
     debug("which plymouth exit code: {!s}".format(isPlymouth))
 
-    return isPlymouth
+    return isPlymouth == 0
 
 def modify_mkinitcpio_conf(partitions, root_mount_point):
     """
@@ -127,7 +133,7 @@ def modify_mkinitcpio_conf(partitions, root_mount_point):
     unencrypted_separate_boot = False
 
     # It is important that the plymouth hook comes before any encrypt hook
-    if detect_plymouth() == 0:
+    if detect_plymouth():
         hooks.append("plymouth")
 
     for partition in partitions: