Be less restrictive on 404 result.

src/zc/buildout/networkcache.txt

@@ -126,7 +126,7 @@ It will be downloaded and stored into networkcache:
    Installing download.
    Downloading http://localhost/hello.txt
    Downloading hello.txt from network cache.
-   Failed to download from network cache hello.txt: 404 : Not Found
+   Failed to download from network cache hello.txt:...404...
    Uploading http://localhost/hello.txt into network cache.
    download: Downloaded http://localhost/hello.txt
 
@@ -175,7 +175,7 @@ As one can see, in case if upload is not working, there is no problem with runni
    Updating download.
    Downloading http://localhost/hello.txt
    Downloading hello.txt from network cache.
-   Failed to download from network cache hello.txt: 404 : Not Found
+   Failed to download from network cache hello.txt: ...404...
    Uploading http://localhost/hello.txt into network cache.
    Fail to upload file. [Errno 111] Connection refused
    download: Downloaded http://localhost/hello.txt
@@ -211,7 +211,7 @@ Upload is optional, and then no upload will be tried:
    Updating download.
    Downloading http://localhost/hello.txt
    Downloading hello.txt from network cache.
-   Failed to download from network cache hello.txt: 404 : Not Found
+   Failed to download from network cache hello.txt: ...404...
    download: Downloaded http://localhost/hello.txt
 
 In case if download cache is failing, original resources are used:
@@ -290,7 +290,7 @@ First put not signed file in networkcache:
    Updating download.
    Downloading http://localhost/hello.txt
    Downloading hello.txt from network cache.
-   Failed to download from network cache hello.txt: 404 : Not Found
+   Failed to download from network cache hello.txt: ...404...
    Uploading http://localhost/hello.txt into network cache.
    download: Downloaded http://localhost/hello.txt
 
@@ -512,7 +512,7 @@ Of course eggs are also supported by networkcache:
    Installing eggs.
    Getting distribution for 'demoneeded==1.2c1'.
    Downloading demoneeded-1.2c1.zip from network cache.
-   Failed to download from network cache demoneeded-1.2c1.zip: 404 : Not Found
+   Failed to download from network cache demoneeded-1.2c1.zip: ...404...
    Uploading http://localhost/demoneeded-1.2c1.zip into network cache.
    Got demoneeded 1.2c1.