E3-894: Fix issue where non-existent versions would cause the build to hang

The ultimate issue here was that we performed a
```
cat $( ... ) | sed '1d'
```
and if that inner block was empty, then `cat` reverted to waiting for user input. The
error also came up with non-specified build numbers, so we need to make sure that those
are also being fetched correctly.

The upshot is now `<module>_VERSION` will automatically fetch the correct build number;
the only potential downside is that if we have a newer version in `${E3_SITEMODS_PATH}`
in comparison to `${EPICS_MODULES}` (read: cellMods), then it won't pick that up. However,
this seems to be a pretty special corner case.

require-ess/tools/driver.makefile

@@ -320,6 +320,7 @@ define fetch_module_versions
   lm := $$(shell echo $1 | tr '[:upper:]' '[:lower:]')
   ifneq ($$(strip $$(filter $(INSTALLED_MODULES),$$(lm))),)
     $$(lm)_VERSION := $($1_DEP_VERSION$2)
+    $$(lm)_VERSION := $$(lastword $$(call FETCH_BUILD_NUMBER,$(E3_SITEMODS_PATH),$$(lm)) $$(call FETCH_BUILD_NUMBER,$(EPICS_MODULES),$$(lm)))
     MODULES += $$(lm)
     REQ += $$(lm)
   else
@@ -338,7 +339,10 @@ export REQ
 
 # Fetches the data from .dep files to be parsed by the above
 define fetch_deps
-$(shell cat $(lastword $(wildcard $(addsuffix /$1/$($1_VERSION)/lib/$(T_A)/$1.dep,$(E3_SITEMODS_PATH) $(EPICS_MODULES)))) | sed '1d')
+$(shell cat $(or \
+  $(lastword $(wildcard $(addsuffix /$1/$($1_VERSION)/lib/$(T_A)/$1.dep,$(E3_SITEMODS_PATH) $(EPICS_MODULES)))),\
+  $(error Module '$1' version '$($1_VERSION)' does not exist.)) \
+  | sed '1d')
 endef
 
 # Used to recurse through versions: recursively fetches all of the dependencies
@@ -791,7 +795,7 @@ ${DEPFILE}: ${LIBOBJS} $(USERMAKEFILE)
 # Check dependencies on other module headers.
 	cat *.d 2>/dev/null | sed 's/ /\n/g' | grep -v '$(EPICS_BASE)/include' | sed -n '$(DEP_PARSER)' > $@.tmp
 # Manully added dependencies: ${REQ}
-	@$(foreach m,${REQ},echo "$m $(or $(and $(or $(wildcard $(EPICS_MODULES)/$m/$($m_VERSION)),$(wildcard $(E3_SITEMODS_PATH)/$m/$($m_VERSION))),$($m_VERSION)),$(error REQUIRED module '$m' version '$($m_VERSION)' does not exist))" >> $@.tmp;)
+	@$(foreach m,${REQ},echo "$m $($m_VERSION)" >> $@.tmp;)
 	cat $@.tmp | sort -u >> $@
 
 endif # In O.* directory

tests/test_build.py

@@ -10,9 +10,7 @@ MODULE_VERSION = "0.0.0+0"
 MODULE_VERSION_NO_BUILD = "0.0.0"
 
 RE_MISSING_FILE = "No rule to make target [`']{filename}'"
-RE_MISSING_VERSION = (
-    "REQUIRED module [`']{module}' version [`']{version}' does not exist."
-)
+RE_MISSING_VERSION = "Module '{module}' version '{version}' does not exist."
 
 
 def create_patch_file(path, desc):