only use Recommends where it makes sense

should make buildable on rhel, for example

exiv2.spec

@@ -53,7 +53,11 @@ Requires: %{name}-libs%{?_isa} = %{version}-%{release}
 %package libs
 Summary: Exif and Iptc metadata manipulation library
 # not strictly required, but convenient and expected
+%if 0%{?fedora} > 25
 Recommends: %{name} = %{version}-%{release}
+%else
+Requires: %{name} = %{version}-%{release}
+%endif
 %description libs
 A C++ library to access image metadata, supporting full read and write access
 to the Exif and Iptc metadata, Exif MakerNote support, extract and delete