Further docstring fixes (#969)

Author: adrhill

DifferentiationInterface/src/compat.jl

@@ -5,7 +5,7 @@ macro public(ex)
         elseif Base.isexpr(ex, :tuple)
             ex.args
         else
-            error("something informative")
+            error("Expected a symbol or a tuple of symbols, got $(repr(ex))")
         end
         esc(Expr(:public, args...))
     else

DifferentiationInterface/src/utils/traits.jl

@@ -75,7 +75,7 @@ pushforward_performance(::ReverseMode) = PushforwardSlow()
 pushforward_performance(::SymbolicMode) = PushforwardFast()
 
 function pushforward_performance(backend::Union{AutoSparse, SecondOrder})
-    throw(ArgumentError("Pushforward performance not defined for $backend`."))
+    throw(ArgumentError("Pushforward performance not defined for `$backend`."))
 end
 
 ## Pullback
@@ -108,7 +108,7 @@ pullback_performance(::ReverseMode) = PullbackFast()
 pullback_performance(::SymbolicMode) = PullbackFast()
 
 function pullback_performance(backend::Union{AutoSparse, SecondOrder})
-    throw(ArgumentError("Pullback performance not defined for $backend`."))
+    throw(ArgumentError("Pullback performance not defined for `$backend`."))
 end
 
 ## HVP
@@ -170,7 +170,7 @@ function hvp_mode(ba::SecondOrder)
 end
 
 function hvp_mode(backend::AutoSparse)
-    throw(ArgumentError("HVP mode not defined for $backend`."))
+    throw(ArgumentError("HVP mode not defined for `$backend`."))
 end
 
 ## Inner prep