[Packaging] Cleanup dependencies

- Tweaked the layout a bit with optional part of dependency description.
- Updated descriptions to help understand dependency usage.
- Made intltool and chardet packages optional. This will help with
  installation where these might be missing and are not crucial.
- Remove gettext from dependency as is part of Python.

DEPENDS.md

@@ -12,7 +12,7 @@ All modules will require the [common](#common) section dependencies.
 ## Build
 
 - [setuptools]
-- [intltool] - Translation file tool
+- [intltool] - Optional: Desktop file translation for \*nix.
 - [closure-compiler] - Minify javascript (alternative is [slimit])
 
 ## Common
@@ -20,37 +20,33 @@ All modules will require the [common](#common) section dependencies.
 - [Twisted] _>= 16.6_ - Use `TLS` extras for `service_identity` and `idna`.
 - [OpenSSL] _>= 1.0.1_
 - [pyOpenSSL]
-- [Chardet]
-- [gettext]
-- [PyXDG]
+- [PyXDG] - Access freedesktop.org standards for \*nix.
+- [xdg-utils] - Provides xdg-open for \*nix.
 - [six]
 - [zope.interface]
-- [xdg-utils]
-
-#### Optional
-
-- [setproctitle] - Support correctly naming Deluge processes.
-- [Pillow] - Image library for `.ico` support.
-- [rencode] _>= 1.0.2_ - Encoding library with Python port bundled.
-- [dbus-python]
+- [chardet] - Optional: Encoding detection.
+- [setproctitle] - Optional: Renaming processes.
+- [Pillow] - Optional: Enable `.ico` support.
+- [rencode] _>= 1.0.2_ - Optional: Encoding library (Python port is bundled).
+- [dbus-python] - Optional: Show item location in filemanager.
 
 #### Windows OS
 
 - [pywin32]
 - [certifi]
-- [py2-ipaddress] - Optional for Python 2 IPv6 lookup
+- [py2-ipaddress] - Optional: Add IPv6 lookup for Python 2.
 
 ## Core (deluged daemon)
 
 - [libtorrent] _>= 1.1.1_
-- [GeoIP] - Optional (_Debian: `python-geoip`_)
+- [GeoIP] - Optional: IP address location lookup. (_Debian: `python-geoip`_)
 
 ## GTK UI
 
 - PyGTK
 - [pycairo]
 - [librsvg] _>= 2_
-- [python-appindicator] - Optional
+- [python-appindicator] - Optional: Ubuntu system tray icon.
 
 #### MacOS
 
@@ -64,10 +60,8 @@ All modules will require the [common](#common) section dependencies.
 
 ### Notifications
 
-Optional dependencies for this plugin.
-
-- [pygame] - Sound
-- [python-notify] - Desktop popup
+- [pygame] - Optional: Play sounds
+- [python-notify] - Optional: Desktop popups.
 
 [python]: https://www.python.org/
 [setuptools]: https://setuptools.readthedocs.io/en/latest/
@@ -87,7 +81,6 @@ Optional dependencies for this plugin.
 [setproctitle]: https://pypi.org/project/setproctitle/
 [gtkosxapplication]: https://github.com/jralls/gtk-mac-integration
 [chardet]: https://chardet.github.io/
-[gettext]: https://www.gnu.org/software/gettext/
 [rencode]: https://github.com/aresch/rencode
 [pyxdg]: https://www.freedesktop.org/wiki/Software/pyxdg/
 [six]: https://pythonhosted.org/six/

deluge/common.py

@@ -26,12 +26,16 @@ import sys
 import tarfile
 import time
 
-import chardet
 import pkg_resources
 
 from deluge.decorators import deprecated
 from deluge.error import InvalidPathError
 
+try:
+    import chardet
+except ImportError:
+    chardet = None
+
 try:
     from urllib.parse import unquote_plus, urljoin
     from urllib.request import pathname2url
@@ -983,12 +987,10 @@ def decode_bytes(byte_str, encoding='utf8'):
     elif not isinstance(byte_str, bytes):
         return byte_str
 
-    encodings = [
-        lambda: ('utf8', 'strict'),
-        lambda: ('iso-8859-1', 'strict'),
-        lambda: (chardet.detect(byte_str)['encoding'], 'strict'),
-        lambda: (encoding, 'ignore'),
-    ]
+    encodings = [lambda: ('utf8', 'strict'), lambda: ('iso-8859-1', 'strict')]
+    if chardet:
+        encodings.append(lambda: (chardet.detect(byte_str)['encoding'], 'strict'))
+    encodings.append(lambda: (encoding, 'ignore'))
 
     if encoding.lower() not in ['utf8', 'utf-8']:
         encodings.insert(0, lambda: (encoding, 'strict'))

setup.py

@@ -19,6 +19,7 @@ from distutils import cmd
 from distutils.command.build import build as _build
 from distutils.command.clean import clean as _clean
 from distutils.command.install_data import install_data as _install_data
+from distutils.spawn import find_executable
 from shutil import rmtree
 
 from setuptools import find_packages, setup
@@ -206,8 +207,8 @@ class BuildTranslations(cmd.Command):
         else:
             basedir = os.path.join(self.build_lib, 'deluge', 'i18n')
 
-        if not windows_check():
-            intltool_merge = 'intltool-merge'
+        intltool_merge = 'intltool-merge'
+        if not windows_check() and find_executable(intltool_merge):
             intltool_merge_opts = '--utf8 --quiet'
             for data_file in (desktop_data, appdata_data):
                 # creates the translated file from .in file.