I have been trying to figure out what is going on when I run apt-get update. I've tried going through the sources file and also using the Ubuntu Tweak to clean the sources list, but nothing is working.   When I run apt-get update I get this:  Reading package lists... Done N: Skipping acquire of configured file 'main/binary-i386/Packages' as repository 'https://packages.microsoft.com/repos/vscode stable InRelease' doesn't support architecture 'i386' W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://download.opensuse.org/repositories/home:/Horst3180/xUbuntu_16.04  Release: The following signatures were invalid: KEYEXPIRED 1496576244 W: The repository 'http://ppa.launchpad.net/tualatrix/ppa/ubuntu xenial Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. W: Failed to fetch http://download.opensuse.org/repositories/home:/Horst3180/xUbuntu_16.04/Release.gpg  The following signatures were invalid: KEYEXPIRED 1496576244 E: Failed to fetch http://ppa.launchpad.net/tualatrix/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found W: Some index files failed to download. They have been ignored, or old ones used instead. W: Duplicate sources.list entry http://packages.microsoft.com/repos/vscode stable Release
PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?
What is the unisex form of a word like fisherman? Do you have to use fisherman and fisherwoman separately, or is fisherperson acceptable? I couldn’t find a dictionary with the word …  In general, what do you do when a word does not have a unisex form? Problem  sudo notify-send Test "Hello World"   Displays a notification as expected.  notify-send Test "Hello World"   Does not display a notification.  Further information  Ubuntu version 16.04.  The notifications appear to use notify-osd instead of notification-daemon. Running notify-send appears to launch a notify-osd process under the user that ran notify-send. I'm not sure what dbus is.   No error messages  There are no errors in the syslog. When I run the following code no error messages occur.   #include &lt;libnotify/notify.h&gt; #include &lt;stdio.h&gt; int main() {     gboolean x = notify_init ("Hello world!");     printf( "notify_init: %d\n", x );     NotifyNotification * Hello = notify_notification_new ("Hello world", "This is an example notification.", "dialog-information");     GError *err = NULL;     x = notify_notification_show (Hello, &amp;err);     printf( "notify_notification_show: %d\n", x );     if(err != NULL) {         printf("Error detected!\n");         printf("Error message:%s\n", err-&gt;message);     }     else {         printf("No error detected.\n");     }     g_object_unref(G_OBJECT(Hello));     notify_uninit();     return 0; }   I do not know what I'm doing. Thanks for the help.  Python Notify  In the past, I've used a python program that has working notifications. I tested a hello world notification and it works without sudo!   #!/usr/bin/env python # -*- coding: utf-8 -*- import gi gi.require_version('Notify', '0.7') from gi.repository import Notify  Notify.init("test") n = Notify.Notification.new('test', 'test2') n.set_urgency(Notify.Urgency.CRITICAL)     n.show()   Code from   I am not sure why this works. The python Notify is just wrapping the library used in the C example. I'd prefer not to use python but will if I must.  Edit  The problem occurred again. Resolved by adding urgency critical. How does a non-mathematician go about publishing a proof in a way that ensures it to be up to the mathematical community's standards? I'm a computer science student who is a maths hobbyist. I'm convinced that I've proven a major conjecture. The problem lies in that I've never published anything before and am not a mathematician by profession. Knowing full well that my proof may be fallacious, erroneous, or simply lacking mathematical formality, what advice would you give me? Want to install Ubuntu on Chromebook How to get the current date/time in Java How did Amix Group get this helicarrier? In Deadpool,       A big fight scene takes place in a battered helicarrier at an Amix Group scrap yard.     What is the history of this particular helicarrier? And why in particular was it sent to the Amix Group scrap yard? I have interesting bug that I have experienced before but has gone away on its own. This one is not going away though.  I have a giant stripe or chunks missing from my desert biome, I would say probably 7 chunks long.  I'm guessing the chunks are corrupted or something, what was hoping to figure is whether it can repaired or reverted.  Here is a picture of the problem. How do ideal quotients behave with respect to localization? Suppose $R$ is commutative ring with unity. For ideals $I$, $J \subseteq R$, the ideal quotient $(J:I)$ is $$(J:I) := \{x\in R \, : \, xI \subseteq J\}$$ Let $S\subset R$ be a multiplicative set. When does localization at $S$ commute with taking quotients, i.e. when does the equality $$(S^{-1} J : S^{-1} I) = S^{-1} (J:I)$$ hold? More generally, when is it true that $$S^{-1} \text{Ann}_{R} (M) = \text{Ann}_{S^{-1} R} (S^{-1} M)$$ for an $R$-module $M$? bordermatrix with blocks I need to write a complicated matrix, that has a structure as in the attached picture. Do we have to tune the number of trees in a random forest? When I used  pip install ipython   or  pip install "ipython[notebook]"   I get the following error:  Downloading/unpacking ipython   Downloading ipython-2.3.1-py27-none-any.whl (2.8MB): 2.8MB downloaded Installing collected packages: ipython Cleaning up... Exception: Traceback (most recent call last):   File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main     status = self.run(options, args)   File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 283, in run     requirement_set.install(install_options, global_options, root=options.root_path)   File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1435, in install     requirement.install(install_options, global_options, *args, **kwargs)   File "/usr/lib/python2.7/dist-packages/pip/req.py", line 671, in install     self.move_wheel_files(self.source_dir, root=root)   File "/usr/lib/python2.7/dist-packages/pip/req.py", line 901, in move_wheel_files     pycompile=self.pycompile,   File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 206, in move_wheel_files     clobber(source, lib_dir, True)   File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 193, in clobber     os.makedirs(destsubdir)   File "/usr/lib/python2.7/os.py", line 157, in makedirs     mkdir(name, mode) OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-packages/IPython'  Storing debug log for failure in /home/username/.pip/pip.log   What does this error mean? How do I fix it? Removable singularities and an entire function Function $f(z)$ is an entire function such that $$|f(z)| \le |z^{n}|$$ for $z \in \mathbb{C}$ and some $n \in \mathbb{N}$.  Show that the singularities of the function $$\frac {f(z)}{z^{n}}$$ are removable. What can be implied about the function $f(z)$ if moreover $f(1) = i$? Draw a far-reaching conclusion.  My attempt: If the singularities of $\frac {f(z)}{z^{n}}$ are removable, it is entire (not sure, need help with the justification) and bounded, so constant from Liouville's theorem, the constant value of the funcion is $i$, hence $f(z)=iz^{n}$.   But what about the $n$ here, is it arbitrary? Could somebody help me prove the removability of the singularities and suggest if my attempt is going the right way? Retagging questions in terms of possible answer technologies How to determine a Python variable's type? How do I see the type of a variable whether it is unsigned 32 bit, signed 16 bit, etc.?  How do I view it? Proper use of passive and active voices? Why exactly is work a path function? This might be a stupid question, but why exactly is work a path function?  In school, my teacher said it’s because it depends on the path. She gave an example of walking up a mountain, and said the work you expend depends on the path you take (straight path up or circling up around the mountain). But isn’t the work expended just equal to $E= mgh?$ Cauchy distribution characteristic function When did Captain America learn what happened to Howard Stark? Near the end of Captain America: Civil War we learn that      Howard and Maria Stark were assassinated by the Winter Soldier   and Captain America admits that he already knew.  But how did he find out? I don't recall this being revealed in any of the previous movies, and I can't think of a reason why the characters who already knew would have gone out of their way to tell Steve about it. I've been watching a lot of pro replays ever since the SC2 beta came out, and I've noticed that almost always, when Protoss research upgrades, the shields are the last research chosen. Why is that? Seems to me that if anything, shields should be the most important upgrade, as they affect all Protoss units and buildings. I need to make Windows 7 STOP disabling the wifi adapter when the wired LAN is connected This is a Dell Latitude E6430. There is a setting in the bios to control this behavior and I have DISABLED it but it still happens. I am also running the latest bios.  When I plug in a network cable the wifi adapter becomes disabled. I need it to stay enabled. What else could be making this happen?  EDIT: The reason I need to do this is because with NETSH WLAN commands you can create a wifi hotspot by sharing the internet connection on the wired adapter and broadcasting a ssid on the virtual wifi nic. I do this all the time but it's not working on this laptop. I'm wondering if it's a network security thing where I am. I'm going to try from my hotel tonight and report back.