locale_gen: works with C.UTF-8 (#6774)

* locale_gen: fix

* test working with C.UTF-8

* working with locale eo

* handle C.UTF-8 edge cases

* grammatic pedantism

* add changelog frag

* add doc about specific OS support

* update changelog frag

plugins/modules/locale_gen.py

@@ -35,6 +35,8 @@ options:
             - Whether the locale shall be present.
         choices: [ absent, present ]
         default: present
+notes:
+    - This module does not support RHEL-based systems.
 '''
 
 EXAMPLES = '''
@@ -74,11 +76,10 @@ def is_available(name, ubuntuMode):
     checking either :
     * if the locale is present in /etc/locales.gen
     * or if the locale is present in /usr/share/i18n/SUPPORTED"""
+    __regexp = r'^#?\s*(?P<locale>\S+[\._\S]*) (?P<charset>\S+)\s*$'
     if ubuntuMode:
-        __regexp = r'^(?P<locale>\S+_\S+) (?P<charset>\S+)\s*$'
         __locales_available = '/usr/share/i18n/SUPPORTED'
     else:
-        __regexp = r'^#{0,1}\s*(?P<locale>\S+_\S+) (?P<charset>\S+)\s*$'
         __locales_available = '/etc/locale.gen'
 
     re_compiled = re.compile(__regexp)
@@ -88,7 +89,8 @@ def is_available(name, ubuntuMode):
         if result and result.group('locale') == name:
             return True
     fd.close()
-    return False
+    # locale may be installed but not listed in the file, for example C.UTF-8 in some systems
+    return is_present(name)
 
 
 def is_present(name):
@@ -106,20 +108,6 @@ def fix_case(name):
     return name
 
 
-def replace_line(existing_line, new_line):
-    """Replaces lines in /etc/locale.gen"""
-    try:
-        f = open("/etc/locale.gen", "r")
-        lines = [line.replace(existing_line, new_line) for line in f]
-    finally:
-        f.close()
-    try:
-        f = open("/etc/locale.gen", "w")
-        f.write("".join(lines))
-    finally:
-        f.close()
-
-
 def set_locale(name, enabled=True):
     """ Sets the state of the locale. Defaults to enabled. """
     search_string = r'#{0,1}\s*%s (?P<charset>.+)' % name
@@ -209,7 +197,7 @@ def main():
             # We found the common way to manage locales.
             ubuntuMode = False
         else:
-            module.fail_json(msg="/etc/locale.gen and /var/lib/locales/supported.d/local are missing. Is the package \"locales\" installed?")
+            module.fail_json(msg="/etc/locale.gen and /var/lib/locales/supported.d/local are missing. Is the package 'locales' installed?")
     else:
         # Ubuntu created its own system to manage locales.
         ubuntuMode = True