Do not convert unsigned elements to InfinityRing

[dkrenn]

sage: InfinityRing(x)
A negative finite number
sage: InfinityRing("junk")
A positive finite number

Component: coercion

Author: Jeroen Demeyer

Branch/Commit: u/jdemeyer/do_not_convert_unsigned_elements_to_infinityring @ 93a039f

Reviewer: Ralf Stephan

Issue created by migration from https://trac.sagemath.org/ticket/17825

[jdemeyer]

Description changed:

--- 
+++ 
@@ -1,9 +1,7 @@
-We have
 
 ```
 sage: InfinityRing(x)
 A negative finite number
-sage: InfinityRing(SR.var('q'))
-A negative finite number
+sage: InfinityRing("junk")
+A positive finite number
 ```
-which looks weird.

[jdemeyer]

Author: Jeroen Demeyer

[jdemeyer]

Branch: u/jdemeyer/do_not_convert_unsigned_elements_to_infinityring

[jdemeyer]

Commit: e16686d

[jdemeyer]

New commits:

e16686d

Do not convert unsigned elements to InfinityRing