Can't install postsharp 4.2.25 to Visual Studio 2015 - postsharp

Question

I'm taking an old branch which was using postshare 4.2.25
When I try to build the solution, I've a popup asking to install postsharp. I don't know why, because the solution use nuget package.
Also, this specific version isn't available on their site. But anyway, luckily we stored the package and so I can start the installation
But the problem is that the installation freeze for a long time (around 2 min) when I click next on this step:
After this freeze I've this error in red (which could be translated by: "Operation timeout"):
Any idea ?
I may try another version, but here I need to quickly patch an old version and updating postsharp version is not something you want to do in a patch...
Thank you
EDIT 1
I've see that the installer make a call, and this call never reply
The content of this call is:
POST http://visualstudiogallery.msdn.microsoft.com/services/Release4.svc HTTP/1.1
Content-Type: application/soap+xml; charset=utf-8
Host: visualstudiogallery.msdn.microsoft.com
Content-Length: 885
Expect: 100-continue
Connection: Keep-Alive
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing">
<s:Header>
<a:Action s:mustUnderstand="1">http://tempuri.org/IReleaseService4/Search</a:Action>
<a:ReplyTo>
<a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
</a:ReplyTo>
<a:To s:mustUnderstand="1">http://visualstudiogallery.msdn.microsoft.com/services/Release4.svc</a:To>
</s:Header>
<s:Body>
<Search xmlns="http://tempuri.org/">
<searchText>nuget</searchText>
<whereClause>((Project.Metadata['SupportedVSEditions'] LIKE '%14.0,IntegratedShell;%') OR (Project.Metadata['SupportedVSEditions'] LIKE '%14.0,Pro;%'))</whereClause>
<orderByClause>Project.Metadata['Ranking'] desc</orderByClause>
<locale>1033</locale>
<skip>0</skip>
<take>25</take>
</Search>
</s:Body>
</s:Envelope>